PHP Variable Boolean validation

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using PHP functions to $x compare variables

An expression	GetType ()	empty ()	is_null ()	isset ()	boolean : if ($x)
$x = "";	string	true	false	true	false
$x = null;	null	true	true	false	false
var $x;	null	true	true	false	false
$x  is undefined		true	false	false
$x = Array ();	array	true	false	true	false
$x = false;	boolean	true	false	true	false
$x = true;	boolean	false	false	true	true
$x = 1;	integer	false	false	true	true
$x =;	integer	false	false	true	true
$x = 0;	integer	true	false	true	false
$x =-1;	integer	false	false	true	true
$x = "1";	string	false	false	true	true
$x = "0";	string	true	false	true	false
$x = "1";	string	false	false	true	true
$x = "php";	string	false	false	true	true
$x = "true";	string	false	false	true	true
$x = "false";	String	FALSE	FALSE	TRUE	TRUE

The above is the usual development of the attention, there are questions you can verify the next Kazakhstan welcome

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PHP Variable Boolean validation