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Identity Booleans
is_null($m) returns true if $m is NULL. empty($m) returns true if $m does not exist or equals false. isset($m1[,$m2……]) returns true if $m1, $m2 are set and are not NULL. unset ($m1[,$m2……]) destroys the specified variables.is_array($m) returns true if $m is an array. is_bool($m) returns true if $m is a boolean.
is_float($m), is_double($m) or is_real($m) returns true if $m is a float. is_int($m), is_integer($m) or is_long($m) returns true if $m is an integer. is_numeric($m) returns true if $m is a number or a numeric string. is_object($m) returns true if $m is an object. is_resource($m) returns true if $m is a resource. is_scalar($m) returns true if $m is an integer, float, string or boolean. is_string($m) returns true if $m is a string.
is_callable($m[,$b=false[,&$s]]) returns true if $m can be called as a function. $s stores the callable name. If $b is true, the function returns true as long as $m is a valid function name, even if the function does not exist. It then only rejects non-string variables or invalid arrays. The valid arrays have only two entries, the first of which is an object or a string, and the second a string.
<!DOCTYPE html>
<html>
<head></head>
<body>
<?php
function func() {}
$fv = 'func';
var_dump(is_callable($fv, false, $callable_name));
echo $callable_name. "<br />";
$fv = function(){};
var_dump(is_callable($fv, false, $callable_name));
echo $callable_name. "<br />";
class C{function method(){}}
$obj = new C;
$mv = array('C', 'method');
var_dump(is_callable($mv, false, $callable_name));
echo $callable_name. "<br />";
$mv = array($obj, 'method');
var_dump(is_callable($mv, false, $callable_name));
echo $callable_name. "<br />";
var_dump(is_callable('funX',true, $callable_name));
$fv=10;
var_dump(is_callable($fv, true, $callable_name));
$mv=['CX','methodX'];
var_dump(is_callable($mv, true, $callable_name));
$mv=[1,2,3];
var_dump(is_callable($mv, true, $callable_name));
?>
</body>
</html>bool(true) func bool(true) Closure::__invoke bool(true) C::method bool(true) C::method bool(true) bool(false) bool(true) bool(false)