What is the safest php method to check that a string is a number?

Question

I checked various method (is_numeric, isset), but I'm not sure built methods are safe in any case.

I need it to work even if the variable to check is:

• an empty string
• null/undefined or whatever invalid state possible

Answer 1

I hope this covers all your cases. is_numeric seems safe enough.

$values = [
    0,
    -3232323,
    423432094823904832948234574072357589345789345789345791305432794827342365786345693453417846393,
    123232e43,
    '-1232132132',
    '023',
    'abcdefaf',
    '0xdeadbeef',
    '',
    null
];


foreach ($values as $val) {
    echo var_export($val, true);
    if (is_numeric($val))
        echo " is numeric\n";
    else
        echo " is NOT numeric\n";
}

Output:

0 is numeric
-3232323 is numeric
4.2343209482390483E+92 is numeric
1.23232E+48 is numeric
'-1232132132' is numeric
'023' is numeric
'abcdefaf' is NOT numeric
'0xdeadbeef' is NOT numeric
'' is NOT numeric
NULL is NOT numeric