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[PHP] Email validation considering PHP version

function isValidEmail($email)
{
	if(version_compare(PHP_VERSION, '5.2.0', '>=')
		return filter_var($email, FILTER_VALIDATE_EMAIL);
	else
		return eregi('^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$', $email);
}

[MySQL] How to check if a value is a number

Here it is a function for checking if a field value represent a number. Floating point and negative numbers are also considered.

CREATE FUNCTION IsNumeric (sIn varchar(1024)) RETURNS tinyint
RETURN sIn REGEXP '^(-|\\+){0,1}([0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+|[0-9]+)$';

[PHP] How to test if a string is a number (with localization issues)

If you use is_numeric function, you could note that 45,362.00 or 45.362,00 are not numbers for this function (only one dot is permitted). So here it is a function (taken from this comment) that uses regular expression to extend is_numeric functionality:

function my_is_numeric($value)  {
    $american = preg_match ("/^(-){0,1}([0-9]+)(,[0-9][0-9][0-9])*([.][0-9]){0,1}([0-9]*)$/" ,$value) == 1;
    $world = preg_match ("/^(-){0,1}([0-9]+)(.[0-9][0-9][0-9])*([,][0-9]){0,1}([0-9]*)$/" ,$value) == 1;
   return ($american or $world);
}

$numbers = array("72", "15.3", "45,362.00", "45.362,00", "62.3692,00", "15:15:00", "15,3");
foreach($numbers as $val) 
	echo "$val is numeric? D: ".is_numeric($val)." M:".my_is_numeric($val)."
";

72 is numeric? D: 1 M:1
15.3 is numeric? D: 1 M:1
45,362.00 is numeric? D: M:1
45.362,00 is numeric? D: M:1
62.3692,00 is numeric? D: M:
15:15:00 is numeric? D: M:
15,3 is numeric? D: M:1