How to use in_array function in PHP to find whether a specified value exists in an array

In PHP development, you often need to find whether an array contains a certain value. At this time, you can use the in_array() function provided by PHP to achieve this. This article will introduce how to use the in_array() function to find whether a specified value exists in an array.

The in_array() function is a PHP built-in function used to determine whether a specified value exists in the array. Its syntax is as follows:

bool in_array(mixed $value, array $array [, bool $strict = FALSE ])

This function accepts three parameters, where $value indicates the value to be found, $array indicates the array to be found, and $strict indicates whether strict mode is enabled. If $strict is set to TRUE, it is required that the elements in $value and $array must have equal types in addition to equal values.

When the function is executed successfully, the return value is TRUE, otherwise the return value is FALSE.

The following is a sample code that uses the in_array() function to find whether a specified value exists in an array:

// 定义一个数组
$arr = array('apple', 'banana', 'orange', 'grape');

// 判断数组中是否存在指定值
if (in_array('apple', $arr)) {
    echo '存在'; // 输出：存在
} else {
    echo '不存在';
}

In the above sample code, we first define an array $arr for judging Whether the specified value exists in the array. Then, we use the in_array() function to find whether the value 'apple' exists in the array. Since the value 'apple' does exist in the array, the in_array() function returns TRUE, and we can output the string 'exists'.

In addition, we can also turn on strict mode by setting the third parameter $strict, which requires that elements not only have equal values, but also have equal types. The sample code is as follows:

// 定义一个数组
$arr = array(1, '2', 3);

// 判断数组中是否存在指定值
if (in_array('2', $arr, true)) {
    echo '存在';
} else {
    echo '不存在'; // 输出：不存在
}

In the above sample code, we pass an array $arr containing integer, string and floating point types as a parameter to the in_array() function and set $strict The parameter is TRUE. Then, we use the in_array() function to find whether there is a string value of '2' in the array.

Since the $strict parameter is set to TRUE, the in_array() function compares the types of elements, so it returns FALSE. Because in the $arr array, the type of '2' is string, and what we are looking for is character type '2'.

To sum up, the in_array() function is a very useful function in PHP development and is often used to find whether an array contains a certain value. When using this function, you need to pay attention to the setting of the $strict parameter to avoid unexpected results.

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