PHP array PHP array summary Part 1)

Array
1. The subscript of the array is an integer value or a string type.
eg1． The keys of indexed arrays are ______, and the keys of associative arrays are ______.
2. When a string is used as an index, quotation marks should be added. Constants or variables do not need to be quoted, otherwise they will not compile.
In PHP, a string without quotes will automatically generate a naked string, and PHP may define this constant later. Unfortunately, if you have the same name in your code, then the string will be reassigned.
eg2.// Display all errors
error_reporting(E_ALL);
$arr = array('fruit' => 'apple', 'veggie' => 'carrot');
// Correct
print $arr['fruit']; // apple
print $arr['veggie']; // carrot
// Incorrect. This works but also throws a PHP error of
// level E_NOTICE because of an undefined constant named fruit
//
// Notice: Use of undefined constant fruit - assumed 'fruit' in...
print $arr[fruit] ; // apple
// Let's define a constant to demonstrate what's going on. We
// will assign value 'veggie' to a constant named fruit.
define('fruit','veggie');
// Notice the difference now
print $arr['fruit']; // apple
print $arr[fruit]; // carrot
// The following is okay as it's inside a string. Constants are not
// looked for within strings so no E_NOTICE error here
print "Hello $arr[fruit]"; // Hello apple
// With one exception, braces surrounding arrays within strings
// allows constants to be looked for
print "Hello {$arr[fruit] }"; // Hello carrot
print "Hello {$arr['fruit']}"; // Hello apple
// This will not work, results in a parse error such as:
// Parse error: parse error , expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'
// This of course applies to using autoglobals in strings as well
print "Hello $arr['fruit']";
print "Hello $_GET['foo']";
// Concatenation is another option
print "Hello " . $arr['fruit']; // Hello apple
?>
3. Key value problem
$a['color'] = 'red';
$ a['taste'] = 'sweet';
$a['shape'] = 'round';
$a['name'] = 'apple';
$a[] = 4; // key will be 0
$b[] = 'a'; // key will be 0
$b[] = 'b'; // key will be 1
$b[] = 'c'; // key will be 2
switching = array( 10, // key = 0
5 => 6,
3 => 7,
'a' => 4,
11, // key = 6 (maximum of integer-indices was 5 )
'8' => 2, // key = 8 (integer!)
'02' => 77, // key = '02'
0 => 12 // the value 10 will be overwritten by 12
);
$multi_array = array("red",
"green",
42 => "blue","yellow" => array("apple",9 => " pear","banana","orange" => array("dog","cat","iguana")));
?>
A. $multi_array['yellow']['apple'][0]
B. $multi_array['blue'][0]['orange'][1]
C. $multi_array[3][3][2]
D. $multi_array['yellow']['orange']['cat']
E. $multi_array['yellow']['orange'][1]
--------------------------------To be continued To be continued ------
4.array_walk
5.var_dump
6.array_intersect
7.array_sum
8.array_count_values ​​
9.array_flip
10.natsort
11.ksort(),asort(),krsort (),sort(),usort()
12.array_reverse()
13.array_merge
14.reset
------------------------- ------To be continuedTo be continuedTo be continued------
15.array_combine
16array_count_values ​​
17.array_diff
18.array_filter
19.array_search

The above has introduced PHP arrays (php array summary part 1), including the content of PHP arrays. I hope it will be helpful to friends who are interested in PHP tutorials.