How to reserve an array in php

PHP is a programming language widely used for web development, in which arrays are a very important data type. In actual development, we often need to sort, filter, or deduplicate arrays, but sometimes we also need to reserve arrays so that array elements can be accessed conveniently and quickly in subsequent use. This article will introduce array reservation operations and their applications in PHP.

1. Basic concept of array reservation

In PHP, array reservation is the manual setting of the associated key name of the array. We can manually assign a unique key name to each element in the array so that the corresponding value can be quickly accessed based on the key name in subsequent operations. Array reservation can be done in different ways, such as associative arrays, numerically indexed arrays, indexed arrays, etc.

In an associative array, we can make a reservation by specifying a unique string for each key name, as shown below:

$students = array("Tom"=>"20", "Jerry"=>"22", "Mike"=>"25");

In a numerically indexed array, we can make a reservation by Each element is assigned a unique numeric index for reservation, as shown below:

$fruits = array(0=>"apple", 1=>"banana", 2=>"orange");

In the index array, we can omit the key name and automatically assign an increasing numeric index to each element, as shown below ：

$cities = array("Beijing", "Shanghai", "Guangzhou");

No matter which method is used, array reservation can help us access array elements quickly and improve code running efficiency.

2. Array reservation application

In actual development, we can use array reservation to help us realize the following application scenarios:

2.1 Read a certain Specific elements

Sometimes we only need to get a specific element in the array without traversing the entire array. Using array reservation can help us quickly locate the elements we need and improve code running efficiency. As shown in the following example, we can get the value of the corresponding element by accessing the key name specified in the associative array:

$students = array("Tom"=>"20", "Jerry"=>"22", "Mike"=>"25");
$age = $students["Jerry"];
echo $age; //输出22

2.2 Inserting or deleting elements

Using array reservation can help us quickly insert or delete Remove elements from an array without operating on the entire array. As shown in the following example, insert a new element in the associative array:

$students = array("Tom"=>"20", "Jerry"=>"22", "Mike"=>"25");
$students["Alice"] = "18";
print_r($students);

//输出结果：
//Array
//(
//    [Tom] => 20
//    [Jerry] => 22
//    [Mike] => 25
//    [Alice] => 18
//)

As shown in the following example, delete an element in the index array:

$fruits = array("apple", "banana", "orange");
unset($fruits[1]);
print_r($fruits);

//输出结果：
//Array
//(
//    [0] => apple
//    [2] => orange
//)

2.3 Array merging

Using array reservation can help us retain duplicate key names when merging two arrays. As shown in the following example, we can use the " " operator to merge two associative arrays and retain elements with the same key name:

$arr1 = array("a"=>"apple", "b"=>"banana", "c"=>"orange");
$arr2 = array("a"=>"pear", "d"=>"peach");
$rs = $arr1 + $arr2;
print_r($rs);

//输出结果：
//Array
//(
//    [a] => apple
//    [b] => banana
//    [c] => orange
//    [d] => peach
//)

3. Conclusion

The array is scheduled to be php A very common and practical operation. Whether you are traversing an array, inserting or deleting elements, or merging arrays, you can use array reservation to improve code efficiency and readability. Understanding the basic concepts and application scenarios of array reservation will be one of the indispensable skills for PHP developers.

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