PHP: PHP type comparison tables - Manual (original) (raw)

The following tables demonstrate behaviors of PHP types and comparison operators, for both loose and strict comparisons. This supplemental is also related to the manual section on type juggling. Inspiration was provided by various user comments and by the work over at» BlueShoes.

Before utilizing these tables, it's important to understand types and their meanings. For example, "42" is a string while 42 is an int. [false](reserved.constants.php#constant.false) is abool while "false" is astring.

Note:

HTML Forms do not pass integers, floats, or booleans; they pass strings. To find out if a string is numeric, you may useis_numeric().

Note:

Simply doing if ($x) while $x is undefined will generate an error of level [E_NOTICE](errorfunc.constants.php#constant.e-notice). Instead, consider using empty() orisset() and/or initialize your variables.

Note:

Some numeric operations can result in a value represented by the constant [NAN](math.constants.php#constant.nan). Any loose or strict comparisons of this value against any other value, including itself, but except [true](reserved.constants.php#constant.true), will have a result of [false](reserved.constants.php#constant.false). (i.e. NAN != NAN and NAN !== NAN) Examples of operations that produce [NAN](math.constants.php#constant.nan) include sqrt(-1), asin(2), and acosh(0).

Comparisons of $x with PHP functions

Loose comparisons with ==

| | true | false | 1 | 0 | -1 | "1" | "0" | "-1" | null | [] | "php" | "" | | | --------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | ---------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | ---------------------------------------------------- | ---------------------------------------------------- | | true | true | false | true | false | true | true | false | true | false | false | true | false | | false | false | true | false | true | false | false | true | false | true | true | false | true | | 1 | true | false | true | false | false | true | false | false | false | false | false | false | | 0 | false | true | false | true | false | false | true | false | true | false | false* | false* | | -1 | true | false | false | false | true | false | false | true | false | false | false | false | | "1" | true | false | true | false | false | true | false | false | false | false | false | false | | "0" | false | true | false | true | false | false | true | false | false | false | false | false | | "-1" | true | false | false | false | true | false | false | true | false | false | false | false | | null | false | true | false | true | false | false | false | false | true | true | false | true | | [] | false | true | false | false | false | false | false | false | true | true | false | false | | "php" | true | false | false | false* | false | false | false | false | false | false | true | false | | "" | false | true | false | false* | false | false | false | false | true | false | false | true |

* [true](reserved.constants.php#constant.true) prior to PHP 8.0.0.

Strict comparisons with ===

| | true | false | 1 | 0 | -1 | "1" | "0" | "-1" | null | [] | "php" | "" | | | --------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | -------------------------------------------------- | | true | true | false | false | false | false | false | false | false | false | false | false | false | | false | false | true | false | false | false | false | false | false | false | false | false | false | | 1 | false | false | true | false | false | false | false | false | false | false | false | false | | 0 | false | false | false | true | false | false | false | false | false | false | false | false | | -1 | false | false | false | false | true | false | false | false | false | false | false | false | | "1" | false | false | false | false | false | true | false | false | false | false | false | false | | "0" | false | false | false | false | false | false | true | false | false | false | false | false | | "-1" | false | false | false | false | false | false | false | true | false | false | false | false | | null | false | false | false | false | false | false | false | false | true | false | false | false | | [] | false | false | false | false | false | false | false | false | false | true | false | false | | "php" | false | false | false | false | false | false | false | false | false | false | true | false | | "" | false | false | false | false | false | false | false | false | false | false | false | true |

Found A Problem?

php at benizi dot com ¶

15 years ago

It's interesting to note that 'empty()' and 'boolean : if($x)'
are paired as logical opposites, as are 'is_null()' and 'isset()'.

Jan ¶

19 years ago

Note that php comparison is not transitive:

"php" == 0 => true
0 == null => true
null == "php" => false

frank ¶

18 years ago

A comparison table for <=,<,=>,> would be nice...
Following are TRUE (tested PHP4&5):
NULL <= -1
NULL <= 0
NULL <= 1
!(NULL >= -1)
NULL >= 0
!(NULL >= 1)
That was a surprise for me (and it is not like SQL, I would like to have the option to have SQL semantics with NULL...).

blue dot hirano at gmail dot com ¶

11 years ago

The truth tables really ought to be colorized; they're very hard to read as they are right now (just big arrays of TRUE and FALSE).

Also, something to consider: clustering the values which compare similarly (like is done on qntm.org/equality) would make the table easier to read as well. (This can be done simply by hand by rearranging the order of headings to bring related values closer together).

edgar at goodforall dot eu ¶

16 years ago

Some function to write out your own comparisson table in tsv format. Can be easily modified to add more testcases and/or binary functions. It will test all comparables against each other with all functions. 

<?php
$funcs = array(
        /* Testing equality */
        'eq' => '==',
        'ne' => '!=',
        'gt' => '>',
        'lt' => '<',
        'ne2' => '<>',
        'lte' => '<=',
        'gte' => '>=',
        /* Testing identity */
        'id' => '===',
        'nid' => '!=='
);
class Test {
        protected $a;
        public $b;
        public function __construct($a,$b){
                <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>h</mi><mi>i</mi><mi>s</mi><mo>−</mo><mo>&gt;</mo><mi>a</mi><mo>=</mo></mrow><annotation encoding="application/x-tex">this-&gt;a = </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7778em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">hi</span><span class="mord mathnormal">s</span><span class="mord">−</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">&gt;</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.4306em;"></span><span class="mord mathnormal">a</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>a;
                <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>h</mi><mi>i</mi><mi>s</mi><mo>−</mo><mo>&gt;</mo><mi>b</mi><mo>=</mo></mrow><annotation encoding="application/x-tex">this-&gt;b = </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7778em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">hi</span><span class="mord mathnormal">s</span><span class="mord">−</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">&gt;</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">b</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>b;
        }
        public function getab(){
                return <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>h</mi><mi>i</mi><mi>s</mi><mo>−</mo><mo>&gt;</mo><mi>a</mi><mi mathvariant="normal">.</mi><mi mathvariant="normal">&quot;</mi><mo separator="true">,</mo><mi mathvariant="normal">&quot;</mi><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">this-&gt;a.&quot;,&quot;. </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7778em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">hi</span><span class="mord mathnormal">s</span><span class="mord">−</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">&gt;</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">a</span><span class="mord">.&quot;</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.1667em;"></span><span class="mord">&quot;.</span></span></span></span>this->b;
        }

}
$tst1 = new Test(1,2);
$tst2 = new Test(1,2);
$tst3 = new Test(2,2);
$tst4 = new Test(1,1);

$arr1 = array(1,2,3);
$arr2 = array(2,3,4);
$arr3 = array('a','b','c','d');
$arr4 = array('a','b','c');
$arr5 = array();

$comp1 = array(
        'ints' => array(-1,0,1,2),
        'floats' => array(-1.1,0.0,1.1,2.0),
        'string' => array('str', 'str1', '', '1'),
        'bools' => array(true, false),
        'null' => array(null),
        'objects' => array($tst1,$tst2,$tst3,$tst4),
        'arrays' => array($arr1, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>a</mi><mi>r</mi><mi>r</mi><mn>2</mn><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">arr2, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8389em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.02778em;">rr</span><span class="mord">2</span><span class="mpunct">,</span></span></span></span>arr3, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>a</mi><mi>r</mi><mi>r</mi><mn>4</mn><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">arr4, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8389em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.02778em;">rr</span><span class="mord">4</span><span class="mpunct">,</span></span></span></span>arr5)
);
$fbody = array();

foreach($funcs as <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi><mi>a</mi><mi>m</mi><mi>e</mi><mo>=</mo><mo>&gt;</mo></mrow><annotation encoding="application/x-tex">name =&gt; </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.5782em;vertical-align:-0.0391em;"></span><span class="mord mathnormal">nam</span><span class="mord mathnormal">e</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=&gt;</span></span></span></span>op){
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>f</mi><mi>b</mi><mi>o</mi><mi>d</mi><mi>y</mi><mo stretchy="false">[</mo></mrow><annotation encoding="application/x-tex">fbody[</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mord mathnormal">b</span><span class="mord mathnormal">o</span><span class="mord mathnormal">d</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mopen">[</span></span></span></span>name] = create_function('$a,$b', 'return <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mi>a</mi><mo mathvariant="normal" lspace="0em" rspace="0em">′</mo></msup><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">a &#x27; . </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7519em;"></span><span class="mord"><span class="mord mathnormal">a</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.7519em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">′</span></span></span></span></span></span></span></span></span><span class="mord">.</span></span></span></span>op . ' $b;');
}

$table = array(array('function', 'comp1', 'comp2', 'f comp1 comp2', 'type'));
/* Do comparisons */
$comp2  = array();
foreach($comp1 as <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>y</mi><mi>p</mi><mi>e</mi><mo>=</mo><mo>&gt;</mo></mrow><annotation encoding="application/x-tex">type =&gt; </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8095em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mord mathnormal">p</span><span class="mord mathnormal">e</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=&gt;</span></span></span></span>val){
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mi>o</mi><mi>m</mi><mi>p</mi><mn>2</mn><mo stretchy="false">[</mo></mrow><annotation encoding="application/x-tex">comp2[</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">co</span><span class="mord mathnormal">m</span><span class="mord mathnormal">p</span><span class="mord">2</span><span class="mopen">[</span></span></span></span>type] = $val;
}

foreach($comp1 as <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>k</mi><mi>e</mi><mi>y</mi><mn>1</mn><mo>=</mo><mo>&gt;</mo></mrow><annotation encoding="application/x-tex">key1 =&gt; </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mord mathnormal" style="margin-right:0.03588em;">ey</span><span class="mord">1</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=&gt;</span></span></span></span>val1){
        foreach($comp2 as <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>k</mi><mi>e</mi><mi>y</mi><mn>2</mn><mo>=</mo><mo>&gt;</mo></mrow><annotation encoding="application/x-tex">key2 =&gt; </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mord mathnormal" style="margin-right:0.03588em;">ey</span><span class="mord">2</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=&gt;</span></span></span></span>val2){
                addTableEntry($key1, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>k</mi><mi>e</mi><mi>y</mi><mn>2</mn><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">key2, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mord mathnormal" style="margin-right:0.03588em;">ey</span><span class="mord">2</span><span class="mpunct">,</span></span></span></span>val1, $val2);
        }
}
$out = '';
foreach($table as $row){
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>o</mi><mi>u</mi><mi>t</mi><mi mathvariant="normal">.</mi><mo>=</mo><mi>s</mi><mi>p</mi><mi>r</mi><mi>i</mi><mi>n</mi><mi>t</mi><mi>f</mi><mo stretchy="false">(</mo><mi mathvariant="normal">&quot;</mi></mrow><annotation encoding="application/x-tex">out .= sprintf(&quot;%-20s\t%-20s\t%-20s\t%-20s\t%-20s\n&quot;, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6151em;"></span><span class="mord mathnormal">o</span><span class="mord mathnormal">u</span><span class="mord mathnormal">t</span><span class="mord">.</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mord mathnormal">p</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal">in</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord">&quot;</span></span></span></span>row[0], <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi><mi>o</mi><mi>w</mi><mo stretchy="false">[</mo><mn>1</mn><mo stretchy="false">]</mo><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">row[1], </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">ro</span><span class="mord mathnormal" style="margin-right:0.02691em;">w</span><span class="mopen">[</span><span class="mord">1</span><span class="mclose">]</span><span class="mpunct">,</span></span></span></span>row[2], <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi><mi>o</mi><mi>w</mi><mo stretchy="false">[</mo><mn>3</mn><mo stretchy="false">]</mo><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">row[3], </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">ro</span><span class="mord mathnormal" style="margin-right:0.02691em;">w</span><span class="mopen">[</span><span class="mord">3</span><span class="mclose">]</span><span class="mpunct">,</span></span></span></span>row[4]);
}

print $out;
exit;

function addTableEntry($n1, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi><mn>2</mn><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">n2, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8389em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">n</span><span class="mord">2</span><span class="mpunct">,</span></span></span></span>comp1, $comp2){
        global <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>a</mi><mi>b</mi><mi>l</mi><mi>e</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">table, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">ab</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mpunct">,</span></span></span></span>fbody;
        foreach($fbody as <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>f</mi><mi>n</mi><mi>a</mi><mi>m</mi><mi>e</mi><mo>=</mo><mo>&gt;</mo></mrow><annotation encoding="application/x-tex">fname =&gt; </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mord mathnormal">nam</span><span class="mord mathnormal">e</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=&gt;</span></span></span></span>func){
                        foreach($comp1 as $val1){
  foreach($comp2 as $val2){
                                        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>v</mi><mi>a</mi><mi>l</mi><mo>=</mo></mrow><annotation encoding="application/x-tex">val = </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">v</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>func($val1,$val2);
                                                <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>a</mi><mi>b</mi><mi>l</mi><mi>e</mi><mo stretchy="false">[</mo><mo stretchy="false">]</mo><mo>=</mo><mi>a</mi><mi>r</mi><mi>r</mi><mi>a</mi><mi>y</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">table[] = array(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">ab</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mopen">[</span><span class="mclose">]</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.02778em;">rr</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mopen">(</span></span></span></span>fname, gettype($val1) . ' => ' . sprintval($val1), gettype($val2) .' => ' . sprintval($val2), gettype($val) . ' => ' . sprintval($val), gettype($val1) . "-" . gettype($val2) . '-' . $fname);
                                        }
                        }
        }
}

function sprintval($val){
        if(is_object($val)){
                return 'object-' . $val->getab();
        }
        if(is_array($val)){
                return implode(',', $val);
        }
        if(is_bool($val)){
                if($val){
                        return 'true';
                }
                return 'false';
        }
        return strval($val);
}

?>

Jeroen ¶

2 years ago

Be aware of the difference between checking the *value* of an array item, and checking the *existence* of an array item:
<?php
$arr = [ 
  'x' => 0,
  'y' => null,
];

isset($arr['x']); // true, same as isset(0)
isset($arr['y']); // false, same as isset(null)

array_key_exists('y', $arr); // true, though the value is null
array_key_exists('z', $arr); // false

jerryschwartz at comfortable dot com ¶

20 years ago

In some languages, a boolean is promoted to an integer (with a value of 1 or -1, typically) if used in an expression with an integer. I found that PHP has it both ways:

If you add a boolean with a value of true to an integer with a value of 3, the result will be 4 (because the boolean is cast as an integer).

On the other hand, if you test a boolean with a value of true for equality with an integer with a value of three, the result will be true (because the integer is cast as a boolean).

Surprisingly, at first glance, if you use either < or > as the comparison operator the result is always false (again, because the integer as cast as a boolean, and true is neither greater nor less than true).

mark at theanti dot social ¶

7 years ago

There is also 0.0 which is not identical to 0.

  $x = 0.0; 
  gettype($x); // double
  empty($x); // true
  is_null($x); //false
  isset($x); // true
  is_numeric($x); // true
  $x ? true : false; // false
  $x == 0; // true
  $x == "0"; // true
  $x == "0.0"; // true
  $x == false; // true
  $x == null; // true
  $x === 0; // false
  $x === false; // false
  $x === null; // false
  $x === "0"; // false
  $x === "0.0"; // false