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>

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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>

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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>

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for loop:

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

Using loops:

<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:

<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>

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