How to create and use associative arrays in php

Associative array is a data type, which is characterized by storing and accessing data through key-value pairs. In PHP, use the array() function to create an array, and the values ​​in the array can be accessed by key name. In this article, we will explain how to create and use associative arrays in PHP.

1. Create an associative array

In PHP, the syntax format for creating an associative array is: $arrayName = array(key1=>value1, key2=>value2, key3=>value3,...). Among them, key is the key name in the associative array, and value is the value in the associative array.

The following is a simple PHP associative array example:

<?php $student = array(
   "name" => "Tom",
   "age" => 20,
   "gender" => "Male"
);
?>

In the above example, we created an associative array named $student and set the three elements to name , age and gender. In PHP, key names are of type string.

2. Accessing associative arrays

To access values ​​in associative arrays through key names, you can use the subscript operator []. For example, to access the name value in the $student array, you would use the following code:

echo $student["name"];

The above code will output the string "Tom".

If the key name does not exist in the array, a warning will be generated. If you need to determine whether the key name exists, you can use the isset() function. For example, the following code checks whether age exists in the $student array:

if (isset($student["age"])) {
   echo "The age of student is " . $student["age"];
} else {
   echo "The age is not set.";
}

3. Modify the associative array

To modify the element value in the associative array, you can use the subscript Operator[] accesses a keyword and sets it to a new value. For example, the following code will modify the age in the $student array:

$student["age"] = 21;

The above code will modify the value of the age element in the $student array from 20 to 21.

4. Delete associative array

To delete elements from an associative array, you can use the unset() function. For example, the following code will delete the gender element from the $student array:

unset($student["gender"]);

Note that the unset() function will not generate any errors if you delete a key that does not exist.

5. Iterate through the associative array

Use the foreach loop to iterate through the entire associative array. For example, the following code will iterate through all the elements in the $student array, and then print out each key name and key value in the array:

foreach ($student as $key => $value) {
   echo "The key of student is " . $key . ", and the value is " . $value . "<br>";
}

The above code will output the following:

The key of student is name, and the value is Tom
The key of student is age, and the value is 21

Summary

This article explains how to create, access, modify, delete, and iterate associative arrays in PHP. Associative arrays are a very common data type that allow quick access to data through key names. When writing PHP programs, mastering the basic usage of associative arrays can improve the efficiency and readability of your code. If you are a beginner in PHP, I hope this article will be helpful to you.

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