How to determine whether a certain value exists in an array in php

In PHP programming, array is a very common data type that can store multiple values, and these values ​​can be of different data types. In actual development, we often need to perform various operations on arrays, including determining whether a value is in the array.

Let’s discuss how to determine whether a value exists in an array in PHP.

1. in_array function

The in_array() function is a function built into PHP to determine whether a value is in an array. Its syntax is as follows:

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

Among them, $needle represents the value to be judged, $haystack represents the array to be judged, and $strict represents whether to use strict mode for comparison (the default is false, that is, strict mode is not used).

The following is an example of a simple in_array() function:

$a = array('apple', 'banana', 'orange');
if (in_array('banana', $a)) {
    echo "存在";
} else {
    echo "不存在";
}

The output result is: "Exists".

2. array_search function

The array_search() function is similar to the in_array() function. It is also a function used to determine whether a value is in an array. The difference is that array_search() The function will return the key name (i.e. subscript) of the found value in the array, or false if it is not found.

The syntax is as follows:

mixed array_search ( mixed $needle , array $haystack [, bool $strict = FALSE ] )

The following is an example of a simple array_search() function:

$a = array('apple', 'banana', 'orange');
$key = array_search('banana', $a);
if ($key !== false) {
    echo "存在，键名为：$key";
} else {
    echo "不存在";
}

The output result is: "Exists, key name: 1".

3. isset function

isset() function is used to determine whether a variable exists, and can also be used to determine whether a value is in an array. The syntax is as follows:

bool isset ( mixed $var [, mixed $... ] )

Among them, $var represents the variable or value to be judged, and $... represents multiple optional variables or values.

The following is an example of a simple isset() function:

$a = array('apple', 'banana', 'orange');
if (isset($a[1])) {
    echo "存在";
} else {
    echo "不存在";
}

The output result is: "Exists".

4. array_key_exists function

array_key_exists() function is a function used to determine whether the specified key name (i.e., subscript) exists in the array. Its syntax is as follows:

bool array_key_exists ( mixed $key , array $array )

Among them, $key represents the key name to be judged, and $array represents the array to be judged.

The following is an example of a simple array_key_exists() function:

$a = array('a' => 'apple', 'b' => 'banana', 'c' => 'orange');
if (array_key_exists('b', $a)) {
    echo "存在";
} else {
    echo "不存在";
}

The output result is: "Exists".

Summary

The above is the method for determining whether a certain value exists in an array in PHP, including the in_array() function, array_search() function, isset() function and array_key_exists() function. In actual development, we can choose the appropriate method to make judgments according to needs.

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