How to determine whether a string is in an array in php

In PHP, there are many methods that can be used to determine whether a string is within an array. In actual programming, this requirement is very common. Here are some common judgment methods:

1. in_array function

There is a built-in function in PHP called in_array, and its syntax is:

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

The needle parameter is the element to be found, and the haystack parameter is the array to search. Returns TRUE if needle is found, FALSE otherwise. If the strict parameter is set to TRUE, the in_array function will check whether the type and value of needle are equal at the same time.

The following is an example:

<?php

$cars = array("Volvo", "BMW", "Toyota");

if (in_array("BMW", $cars)) {

echo "Found BMW!";

}

else{

echo "BMW not found!";

}

?>

The output result is: Found BMW!

2. array_search function

There is another one in PHP The built-in function is called array_search, and its syntax is:

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

This function is similar to the in_array function, but different What it does is it returns the subscript of the element in the array. If the element does not exist in the array, returns FALSE. The following is an example:

<?php

$cars = array("Volvo", "BMW", "Toyota");

$pos = array_search("BMW", $cars);

if ($pos !== false) {

echo "Found BMW at index " . $pos;

}

else{

echo "BMW not found!";

}

?>

The output result is: Found BMW at index 1

3. Notes when using in_array and array_search

When using in_array When using the array_search function, there are several things to note:

1) If you want to check whether a string exists in the array, you need to ensure that the elements in the array are of string type. Otherwise, the strict parameter is required, set to TRUE.

2) The in_array and array_search functions are case-sensitive. If you want to ignore case, you can use the array_map function to convert all elements in the array to lowercase or uppercase before searching.

3) If you want to determine whether a string is not in an array, you can use !in_array or array_search === false.

Summary:

Determining whether a string is in an array is a common requirement in PHP programs. In PHP, you can use the in_array and array_search functions for quick judgment. When using these two functions, you need to pay attention to the type and case of the parameters.

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