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This tutorial will discuss different ways to check for numeric characters in PHP. We will use regular expressions and built-in functions in PHP.

The functions we will use are ctype_digit, preg_match, , strpos, is_numericand filter_var. These methods are useful because they allow you to exclude some non-numeric characters.

ctype_digitChecking for numeric characters in PHP using

ctype_digitThe function accepts a text string and checks whether all string characters are digits. ctype_digitExponentiation characters are not considered digits.

example:

<?php
    $number_with_exponent = '53e10';

    if (ctype_digit('$number_with_exponent')) {
        echo $number_with_exponent . ' contains numerical characters';
    } else {
        echo $number_with_exponent . ' contains non-numeric characters';
    }
?>

Output:

53e10 contains non-numeric characters

The function will return falseas the string has exponential characters.

Checking for numeric characters using regular expressions in PHP

A regular expression can check if all characters in a string are digits. The first thing you must do is set up a match pattern that specifically matches digit characters.

In the code block, we preg_matchset up the regular expression matching pattern using the PHP function, and then we pass the string to be checked as the second parameter to preg_matchthe function.

example:

<?php
    $number_with_exponent = '53e10';

    if (preg_match("/^\-?[0-9]*\.?[0-9]+\z/", $number_with_exponent)) {
        echo $number_with_exponent . ' contains numerical characters';
    } else {
        echo $number_with_exponent . ' contains non-numeric characters';
    }
?>

Output:

53e10 contains non-numeric characters

Checking for numeric characters excluding exponential sign in PHP

You'll find this approach useful if you use ifthe statement with the function. When you use the function on a string that contains an exponential symbol, the function will return 0 because PHP considers the exponential symbol to be a valid numeric character.is_numericis_numerictrue

example:

<?php
    $number_with_exponent = '53e10';
    $check_string_position = strpos($number_with_exponent, 'e');
    $check_is_numeric = is_numeric($number_with_exponent);

    if ($check_string_position === false && $check_is_numeric) {
        echo $number_with_exponent . ' contains numerical characters';
    } else {
        echo $number_with_exponent . ' contains non-numeric characters';
    }
?>

Output:

53e10 contains non-numeric characters

filter_varChecking for numeric characters in PHP using the

The PHP filter_varfunction will filter the variable according to the filter. You provide this filter as the second parameter to filter_varthe function.

To check for numeric characters, you will use FILTER_VALIDATE_INTa filter called .

example:

<?php
    $test_numbers = ['53e10', '3.5', '2x3', '200'];

    foreach ($test_numbers as $value) {
        $check_integer = filter_var($value, FILTER_VALIDATE_INT);
        if ($check_integer === false) {
            echo $value . ' contains non-numeric characters' . "<br/>";
        } else {
            echo $value . ' contains numerical characters' . "<br/>";
        }
    }
?>

Output:

53e10 contains non-numeric characters <br />
3.5 contains non-numeric characters <br />
2x3 contains non-numeric characters <br />
200 contains numerical characters <br />