How to convert string to integer variable in PHP

In PHP, converting a string into an integer variable is a very basic operation, which is very common in program development. This article will introduce how to convert a string into an integer variable in PHP.

First of all, we need to know that in PHP, there are two methods to convert strings into integer variables, namely intval() function and (int) force Type conversion. Below we introduce these two methods respectively.

1. intval() function

intval() function is a function that comes with PHP. Its function is to convert the specified string into an integer (integer type variable) and return the transformed result. The syntax of this function is as follows:

intval(string $string, int $base = 10): int

Among them, $string represents the string to be converted into an integer, $base represents the base, which can be an integer between 2 and 36 (default is 10). The value returned by this function is an integer variable.

For example:

$num1 = "123";
$num2 = "0x1a";
$num3 = "10000";
$num4 = "999999999999999999999999";
$num5 = "hello";

echo intval($num1) . "<br>";  // 输出: 123
echo intval($num2, 16) . "<br>";  // 输出: 26 
echo intval($num3) . "<br>";  // 输出: 10000
echo intval($num4) . "<br>";  // 输出: 2147483647  （因为超过了 int 类型的最大值）
echo intval($num5) . "<br>";  // 输出: 0

2. (int) Forced type conversion

In PHP, we can also use forced type conversion to convert a string into an integer variable. The syntax is (int)$string, where $string represents the string to be converted. This method actually converts the part of the string starting from the first valid numeric character until it encounters a non-numeric character into an integer variable.

For example:

$num1 = "123";
$num2 = "0x1a";
$num3 = "10000";
$num4 = "999999999999999999999999";
$num5 = "hello";

echo (int)$num1 . "<br>";  // 输出: 123
echo (int)$num2 . "<br>";  // 输出: 0  （因为 0x1a 中的非数字字符 'x' 没有被转化）
echo (int)$num3 . "<br>";  // 输出: 10000
echo (int)$num4 . "<br>";  // 输出: -1  （因为超过了 int 类型的最大值，转化成负数）
echo (int)$num5 . "<br>";  // 输出: 0  （因为第一个有效数字字符是 'h'，找不到有效数字）

To sum up, the above are the two methods of converting strings into integer variables in PHP. Developers can choose different methods according to their needs.

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