PHP Array Summary chapter (i) _php tips

Array
1. The subscript of an array is an integer value or a string type.
Eg1. The key of the indexed array is ___, and the key of the associative array is ___.
2. When the string is indexed, enclose the quotation marks. A constant or variable cannot be compiled without quotation marks.
In PHP, a string without quotes will automatically generate a raw string, and PHP may define the constant later, unfortunately, if you have the same name in your code, the string is then assigned a new value.
eg2.<?php
Show All Errors
Error_reporting (E_all);
$arr = Array (' Fruit ' => ' apple ', ' veggie ' => ' carrot ');
That's right
Print $arr [' fruit ']; Apple
Print $arr [' Veggie ']; Carrot
Not correct. This works but also throws a PHP error of
Level e_notice because of 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
Would 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 $arr [fruit]"; Hello Apple
With one exception, braces surrounding arrays within strings
Allows constants to is looked for
Print "Hello {$arr [fruit]}"; Hello Carrot
Print "Hello {$arr [' Fruit ']}"; Hello Apple
This is not work, results in a parse error such as:
Parse error:parse error, expecting t_string ' or t_variable ' or t_num_string '
This is course applies to using autoglobals in strings as
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 would be 0
$b [] = ' a '; Key would be 0
$b [] = ' B '; Key would be 1
$b [] = ' C '; Key would be 2
switching = Array (ten,//key = 0
5 => 6,
3 => 7,
' A ' => 4,
One,//key = 6 (maximum of integer-indices was 5)
' 8 ' => 2,//key = 8 (integer!)
' => ',//key = ' 02 '
0 =>//The value of is overwritten by 12
);
<?php
$multi _array = Array ("Red",
"Green",
=> "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------
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 continued------
15.array_combine
16array_count_values
17.array_diff
18.array_filter
19.array_search