How to check if string contains only numeric digits in PHP ?

Given a string, the task is to check whether the string contains only numeric digits in PHP. It is a common task to verify whether a given string consists of only numeric digits in PHP. It can be useful when dealing with user input validation, form submissions, or data processing tasks where numeric values are expected.

For instance, the below examples illustrate the concept:

Input: str = "1234"
Output: true

Input: str = "GeeksforGeeks2020" 
Output: false 

Here, we will cover three common scenarios for checking if the string contains only numeric digits.

Using ctype_digit Function

PHP provides a built-in function called ctype_digit() that can be used to check if all characters in a string are numeric digits.

Example: This example illustrates checking if string contains only numeric digits using ctype_digit Function in PHP.

<?php

function isNumeric($str)
{
    return ctype_digit($str);
}

// Driver code
$str1 = "12345";
$str2 = "gfg123";

echo isNumeric($str1) ? "Numeric String" : "Non Numeric String";
echo "\n";
echo isNumeric($str2) ? "Numeric String" : "Non Numeric String";
?>

Numeric String
Non Numeric String

Using Regular Expressions

Regular expressions provide a powerful way to validate and manipulate strings. The preg_match() function can be used to check if a string contains only numeric digits.

Example: This example illustrates checking if string contains only numeric digits using the Regular Expressions.

<?php

function isNumeric($str)
{
    return preg_match('/^[0-9]+$/', $str);
}

// Driver code
$str1 = "12345";
$str2 = "abc123";

echo isNumeric($str1) ? "Numeric String" : "Non Numeric String";
echo "\n";
echo isNumeric($str2) ? "Numeric String" : "Non Numeric String";

?>

Numeric String
Non Numeric String

Using is_numeric Function

The is_numeric() function in PHP checks if a variable is a numeric value or a numeric string.

Example: This example illustrates checking if string contains only numeric digits using the is_numeric Function.

<?php

function isNumeric($str)
{
    return is_numeric($str);
}

// Driver code
$str1 = "12345";
$str2 = "abc123";

echo isNumeric($str1) ? "Numeric String" : "Non Numeric String";
echo "\n";
echo isNumeric($str2) ? "Numeric String" : "Non Numeric String";
?>

Numeric String
Non Numeric String

Using filter_var Function

The filter_var() function in PHP can be used with the FILTER_VALIDATE_INT filter to check if a string contains only numeric digits. This method converts the string to an integer and validates it.

Example: This example illustrates checking if a string contains only numeric digits using the filter_var Function.

<?php 
  
function isNumeric($str) 
{ 
    return filter_var($str, FILTER_VALIDATE_INT) !== false; 
} 
// Nikunj Sonigara
// Driver code 
$str1 = "12345"; 
$str2 = "abc123"; 
  
echo isNumeric($str1) ? "Numeric String" : "Non Numeric String"; 
echo "\n"; 
echo isNumeric($str2) ? "Numeric String" : "Non Numeric String"; 
?>

Numeric String
Non Numeric String

Using strspn Function

The strspn() function in PHP returns the length of the initial segment of a string consisting entirely of characters contained within a given mask. We can use this to check if the string contains only numeric digits.

Example:

<?php
$str = "1234";
if (strspn($str, '0123456789') == strlen($str)) {
    echo "true";
} else {
    echo "false";
}
?>

true

Using array_filter and is_numeric

Another valid approach to check if a string contains only numeric digits in PHP is to convert the string into an array of characters and use the array_filter function in combination with is_numeric. This method iterates through each character and verifies if each one is a numeric digit.

Example

<?php
function isNumericString($str) {
    // Convert the string to an array of characters
    $charArray = str_split($str);

    // Use array_filter to keep only numeric characters
    $numericArray = array_filter($charArray, 'is_numeric');

    // Check if the filtered array has the same length as the original string
    return count($charArray) === count($numericArray);
}


$input1 = "1234";
$input2 = "GeeksforGeeks2020";

echo "Input: $input1\n";
echo "Output: " . (isNumericString($input1) ? 'true' : 'false') . "\n";

echo "Input: $input2\n";
echo "Output: " . (isNumericString($input2) ? 'true' : 'false') . "\n";
?>

Input: 1234
Output: true
Input: GeeksforGeeks2020
Output: false