How to verify whether a string is an even number in php

PHP is a widely used open source scripting language that can easily handle strings, values, variables, etc. In PHP, verifying whether a string is an even number is a common need. This article will introduce several methods to solve this problem.

Method 1: Use the modulo operator

In PHP, you can use the modulo operator (%) to determine whether a number is even. If an even number is divided by 2 and the remainder is 0, you can use this feature to verify whether the string is even.

For example, the following code snippet can verify whether a string is an even number:

<?php
$str = "2468";
if ($str % 2 == 0) {
    echo "是偶数";
} else {
    echo "不是偶数";
}
?>

The running result is:

是偶数

In this example, the string is assigned to the variable $ str and then use the modulo operator (%) to convert the string to an integer and check if it is an even number. If the remainder is 0, the string is even, otherwise it is odd.

Method 2: Use PHP functions

In addition to directly using the modulo operator, PHP also provides several functions to determine whether a string is an even number.

1. Use the intval() function

You can use the intval() function to convert a string into an integer and check whether the integer is an even number.

For example, the following code snippet can verify whether a string is an even number:

<?php
$str = "2468";
if (intval($str) % 2 == 0) {
    echo "是偶数";
} else {
    echo "不是偶数";
}
?>

The running result is:

是偶数

In this example, use the intval() function to convert the characters into The string is converted to an integer and checked for evenness using the modulo operator (%).

2. Use the preg_match() function

You can also use the preg_match() function to perform regular expression matching on a string and check whether the string is an even number.

For example, the following code snippet can verify whether a string is an even number:

<?php
$str = "2468";
if (preg_match(&#39;/^[0-9]*[02468]$/&#39;, $str)) {
    echo "是偶数";
} else {
    echo "不是偶数";
}
?>

The running result is:

是偶数

In this example, use the regular expression /^[ 0-9]*[02468]$/ matches a string starting with a number and ending with an even number.

Method 3: Using bitwise operators

Another way to verify whether a string is an even number is to use bitwise operators. In PHP, you can use the bitwise AND operator (&) to convert a string to binary and check if the last bit is 0.

For example, the following code snippet can verify whether a string is an even number:

<?php
$str = "2468";
if ($str & 1 == 0) {
    echo "是偶数";
} else {
    echo "不是偶数";
}
?>

The result is:

是偶数

In this example, the bitwise AND operation is used Convert the string to binary using the ampersand (&) and check if the last bit is 0, if so, the string is even.

Conclusion

Whether you use the modulo operator or a function, PHP provides a variety of ways to verify whether a string is even. During the development process, you can choose the most appropriate method based on your needs.

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