Check if String Starts With a Number in PHP

This tutorial will discuss about unique ways to check if string starts with a number in php.

Table Of Contents

Method 1: Using Regex

PHP provides a function preg_match(), it accepts a regex pattern as first parameter and a string as the second parameter. If the string matches the given regex pattern, then it returns 1 otherwise it returns 0.

We can pass a regex pattern i.e. “/^[0-9]/” and given string into the preg_match() function, and if it returns 1, then it means that the string starts with a number. We have created a function for the same,

function startsWithNumber($str)
{
    return preg_match('/^[0-9]/', $str) === 1;
}

This function accepts a string as an argument and returns true if the string starts with the a number.

Let’s see the complete example,

<?php
/**
 * Checks if a string starts with a number using
 * regular expressions (preg_match()).
 *
 * @param string $str The string to check.
 * @return bool True if the string starts with a number, false otherwise.
 */
function startsWithNumber($str)
{
    return preg_match('/^[0-9]/', $str) === 1;
}

$strValue = "221B Baker Street";

// Check if there is a Number at the beginning of String
if (startsWithNumber($strValue)) {
    echo "The string starts with a number.";
} else {
    echo "The string does not start with a number.";
}
?>

Output

The string starts with a number.

Method 2: Using is_numeric() & ctype_digit() functions

The is_numeric() function accepts a variable as an argument and returns true, if the given variable is either in number or a number string. So we can use this to check if the first character of the string is a number or not. But with this, we need also need to use the ctype_digit() function. It accepts a string as an argument and returns true if all the characters in the provided string are numericals.

So we have created a function which accepts a string as an argument end returns true if the given string starts with a number i.e.

function startsWithNum($str)
{
    $firstChar = $str[0];
    return is_numeric($firstChar) && ctype_digit($firstChar);
}

Inside this function, we will fetch the first character of the string and then we will use the is_numeric() and ctype_digit() functions to check if the string starts with a numeric digit.

In the below example we will use this function to check if the string starts with a given number with any number in PHP

Let’s see the complete example,

<?php
/**
 * Checks if a string starts with a number using
 * is_numeric() and ctype_digit().
 *
 * @param string $str The string to check.
 * @return bool True if the string starts with a number, false otherwise.
 */
function startsWithNum($str)
{
    $firstChar = $str[0];
    return is_numeric($firstChar) && ctype_digit($firstChar);
}

$strValue = "221B Baker Street";

// Check if there is a Number at the beginning of String
if (startsWithNum($strValue)) {
    echo "The string starts with a number.";
} else {
    echo "The string does not start with a number.";
}
?>

Output

The string starts with a number.

Summary

Today, we learned about two ways to check if string starts with a Number in PHP.