php data operation

The most comprehensive introduction to array functions: http://cn2.php.net/manual/zh/book.array.php, frequently used notes.

Declaration:

$array = array("id" => 1, "name" => "duanyong");

Get all keys:

$key = array_keys($ array);

Get all values:

$values ​​= array_values($array);

Iterate over values ​​and values:

a. foreach ($array as $key => $value) {
echo $key . "t" . $value;
}

b. while (list($key, $value) = each($array)) {
echo $key . "t" . $value;
}

Retrieve data
in_array() and array_search(), if the third parameter is specified as true, then strict checking will be performed (for example, if there is a string of 1 in the array, but the search uses the number 1, if the third parameter is not specified, it will Returns true, otherwise false).
in_array("duanyong", array("aaaa", "bbbb", "duanyong")); //Check whether the string duanyong exists in the array
array_search("duanyong", array("id" => " 1", "sex" => 1, "name" => "duanyong"), true); //Return the key after finding the value, otherwise return false

Check whether the index exists
$array = array ("name" => null);
isset($array["name"]); //return false
array_key_exists("name", $array); //return true

Array pointer operations

Special attention should be paid to the fact that if the pointer has moved outside the data subscript, you need to use reset to reset the array pointer (put it on the first element) before you can continue the operation, otherwise an accident will occur.
current($array); //Return the current element
next($array); //Return the next element, no false is returned
prev($array); //Return the previous element, no false is returned
end($ array); //Return the last element
reset($array); //Place the pointer on the first element

Array sorting
Type of sort:
• SORT_REGULAR - Normal comparison unit (does not change type)
  •       SORT_NUMERIC      - Cells are compared as numbers
    •       SORT_STRING     - Cells are compared as strings
    •   SORT_LOCALE_STRING   - Cells are compared as strings according to the current locale settings. New in PHP 4.4.0 and 5.0.2. Prior to PHP 6, the system locale was used, which could be changed with setlocale(). Since PHP 6, the i18n_loc_set_default() function must be used.

Sort the data by value and maintain the key-value relationship
asort, arsort

Sort the data by key and maintain the key-value relationship
ksort, krsort

Sort the data while discarding the keys and generate a new data index
sort, resort

sorted by user rules, usort will delete the original index, uksort and uasort will keep the original index
usort, uksort, uasort

array filter
array_filter() If the filter function is not specified, the element Boolean value will be returned as true elements