Introduction to the usage of PHP in_array() function

In PHP applications, we often need to find a specific value in an array. In order to conveniently find whether a specified value exists in an array in PHP, we can use the in_array() function. In this article, we will delve into the syntax, parameters, and usage of this function.

The syntax of the in_array() function

The basic syntax of the in_array() function is as follows:

in_array($needle,$haystack,$strict);

Parameter description:

$needle: the value to be found , can be any type of data.

$haystack: The array to be searched, usually an array.

$strict: Optional parameter, if type comparison is required, this parameter should be set to true (strict mode).

The return value of the in_array() function

If $needle is found in the $haystack array, it returns true, otherwise it returns false.

Usage of in_array() function

Let us look at a few examples to demonstrate the different uses of in_array() function:

Example 1:

Let's first look at a simple example:

$fruits = array("apple", "banana", "orange");
if (in_array("banana", $fruits)) {
  echo "找到了 banana";
} else {
  echo "没有找到 banana";
}

In this example, we first create a fruit array containing three elements. We then use the in_array() function to find if an element named "banana" is in the array. Finally, we output the result "found banana".

Example 2:

Next, let’s look at a slightly more complex example. This example can check whether the value is in the array, and if so, it can return the matching key name.

$age = array("Peter"=>"35", "Victor"=>"27", "kyle"=>"30");
if (in_array("35", $age)) {
  echo "找到了35所对应的键名是：" . array_search(35, $age);
}

Here, we create an associative array $age, which contains three key-value pairs. We then use the in_array() function to find if there is an element with a value of "35" in the array. If found, use the array_search() function to return the key name of "35". Finally, we output "The key name corresponding to 35 was found: Peter", indicating that the matching key name was found.

Example 3:

In the last example, we try to use the in_array() function to find the number 9 in the array $numbers.

$numbers = array("1", "2", "3", "5", "7");
if (in_array("9", $numbers)) {
  echo "找到了9";
} else {
  echo "没有找到9";
}

Since there is no number 9 in the array $numbers, "9 not found" will be output in this example.

The in_array() function in strict mode

By default, the in_array() function does not consider types when comparing values. Therefore, in the following example, both the string "2" and the number 2 will be considered to exist in the array.

$numbers = array("1", "2", "3", "5", "7");
if (in_array("2", $numbers)) {
  echo "找到了2";
} else {
  echo "没有找到2";
}

However, if you need to consider data types when comparing, you must use strict mode in the function. In strict mode, only values ​​of the same type will match successfully. To use strict mode, set the $strict parameter to true.

$numbers = array("1", "2", "3", "5", "7");
if (in_array(2, $numbers, true)) {
  echo "找到了2";
} else {
  echo "没有找到2";
}

In this example, the in_array() function will compare the data types directly, so only the number 2 will match successfully.

Use the in_array() function to determine whether multiple values ​​exist in the array

If you need to determine whether multiple values ​​exist in the array at the same time, you can use a loop structure or the in_array() function and logic Operators are combined to make judgments. The following is an example of using the in_array() function to determine whether multiple values ​​exist in an array:

$numbers = array("1", "2", "3", "5", "7");
if (in_array("2", $numbers) && in_array("3", $numbers)) {
  echo "同时找到了 2 和 3";
}

In this example, the in_array() function will check whether the numbers 2 and 3 are both contained in the array. Returns true if both values ​​exist.

Summary

In this article, we took an in-depth study of the syntax, parameters, and usage of the in_array() function. We learned how to find a specified value in an array, how to use strict mode, and how to check if multiple values ​​are present in an array at the same time. I hope this article can help you better understand the usage of the in_array() function and write PHP code more efficiently.

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