php array query content

In PHP, an array is a special data type used to store multiple data. In practical applications, arrays need to be queried and traversed frequently. The following will introduce some methods and techniques of PHP array query.

1. Querying array elements

Querying array elements is one of the most commonly used operations. The value of an array element can be obtained in the following two ways:

1. Using square bracket syntax ("[ ]"):

   <code>$colors = array("red", "green", "blue"); 
   echo $colors[1]; // 输出 "green"</code>

2. Using association Get the value from the key name of the array:

   <code>$my_arr = array("name" => "Tom", "age" => 25, "gender" => "male"); 
   echo $my_arr["name"]; // 输出 "Tom"</code>

2. Query the key name or key value of the array

For associative arrays, sometimes you need to query the key name or key value of the array. The following are several practical functions:

1. array_keys() Function:

array_keys() The function returns an array, which contains all the keys in the original array. new array.

<code>$my_arr = array("name" => "Tom", "age" => 25, "gender" => "male");
$keys = array_keys($my_arr);
print_r($keys); // 输出：Array ( [0] => name [1] => age [2] => gender )</code>

2. array_values() Function:

array_values() function returns an array, which contains a new array composed of all key values ​​​​in the original array.

<code>$my_arr = array("name" => "Tom", "age" => 25, "gender" => "male");
$values = array_values($my_arr);
print_r($values); // 输出：Array ( [0] => Tom [1] => 25 [2] => male )</code>

3. in_array() function:

in_array() function checks whether the specified value exists in the array and returns true if it exists, otherwise it returns false.

<code>$colors = array("red", "green", "blue"); 
if(in_array("red", $colors)){
   echo "Red is in the array."; // 输出：Red is in the array.
}</code>

3. Traversing the array

Traversing the array is one of the most basic methods to obtain all elements of the array. The following are several effective methods of traversing an array:

1. ##foreach loop:

   <code>$colors = array("red", "green", "blue"); 
   foreach ($colors as $value) {
   echo "$value <br>";
   }
   // 输出：
   // red
   // green
   // blue</code>

for loop:

can be used A for loop is used to traverse an array. First, you need to get the length of the array, and then use a loop statement to read each element in the array in turn.

<code>$colors = array("red", "green", "blue"); 
for($i = 0; $i < count($colors); $i++) {
    echo $colors[$i]."<br>";
}
// 输出：
// red
// green
// blue</code>

4. Query multi-dimensional array

Multi-dimensional array refers to an array containing multiple array elements, usually a two-dimensional array, a three-dimensional array, etc. Here are several ways to query multidimensional arrays:

Using loops:

For two-dimensional arrays, you can use two for loops to iterate through each element.

<code>$users = array(
   array("John", "Smith", 35),
   array("Jane", "Doe", 28),
   array("Bob", "Johnson", 42),
);

for($row = 0; $row < count($users); $row++) {
   for($col = 0; $col < count($users[$row]); $col++) {
      echo $users[$row][$col]." ";
   }
   echo "<br>";
}

// 输出：
// John Smith 35
// Jane Doe 28
// Bob Johnson 42</code>

Using array functions:

You can use some functions specifically for multi-dimensional arrays to query and operate multi-dimensional arrays, such as the array_walk_recursive() function that can traverse multi-dimensional arrays.

<code>$products = array(
  "Clothing" => array(
     "Men's" => array("Shirts", "Pants", "Jackets"),
     "Women's" => array("Dresses", "Skirts", "Blouses"),
  ),
  "Beauty" => array(
     "Skincare" => array("Facial Cleansers", "Moisturizers", "Masks"),
     "Makeup" => array("Foundation", "Mascara", "Lipstick"),
  )
);

function printValues($value, $key) 
{ 
   echo $key." : ".$value."<br>"; 
}

array_walk_recursive($products, 'printValues');

// 输出：
// Shirts
// Pants
// Jackets
// Dresses
// Skirts
// Blouses
// Facial Cleansers
// Moisturizers
// Masks
// Foundation
// Mascara
// Lipstick</code>

In short, PHP arrays are very powerful and flexible tools that can be used to process a variety of data. For beginners, you may need to learn some basic array operations and functions to query and manipulate arrays efficiently.

The above is the detailed content of php array query content. For more information, please follow other related articles on the PHP Chinese website!