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What are the values and keys of php associative array
- PHPzOriginal
- 2023-04-23 09:16:19667browse
PHP is a widely used open source scripting language that is widely used in the field of website development. Among them, associative array is a very common data type. It is different from ordinary numerical index array in that each element of associative array is identified by a unique key.
Associative array (associative array), also called dictionary or mapping, is a data structure used to store key-value pairs. In PHP, associative arrays can be created using the array() function or the simplified form []. As follows:
$assoc_array = array( "key1" => "value1", "key2" => "value2", "key3" => "value3");
The above code creates an associative array containing three elements. Each element consists of a key and a value. The keys here are "key1", "key2" and "key3" respectively, and the corresponding values are "value1", "value2" and "value3" respectively.
In an associative array, the position of each element is no longer ordered, but is identified and accessed by a key. Therefore, when using associative arrays, there is usually no need to loop through all elements. Instead, the corresponding value can be accessed by key, as shown below:
echo $assoc_array["key1"]; // 输出：value1
The above code will output the value "value1" of the element with key "key1" in the associative array.
In addition to manually defining key-value pairs, PHP also provides some built-in functions that can be used to create common associative arrays, such as array_merge(), array_combine(), etc.
It is worth noting that the keys of associative arrays in PHP can be of any type, including strings, integers, floating point numbers, Boolean values, etc. However, it is important to note that all keys that are not string scalar types will be converted to strings. For example, the following code:
$assoc_array = array( 1 => "value1", 2.1 => "value2", true => "value3");
In the associative array created by the above code, the integer 1 and the floating point number 2.1 are converted into the strings "1" and "2.1" as keys, and the Boolean value true is converted into The string "1" is used as the key. Therefore, these elements can be accessed in the following ways:
echo $assoc_array[1]; // 输出：value1 echo $assoc_array["2.1"]; // 输出：value2 echo $assoc_array[true]; // 输出：value3
In PHP, associative arrays are a very commonly used data type that can flexibly handle various data structures. By grasping the concept of keys and values for associative arrays, we can better use this data type to optimize our code.
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