Introduction to PHP arrays

Array base:     PHP, the subscript of an array can be an integer, or it can be a string     PHP, the element order of the array is not determined by the subscript, but by the order in which it is "joined", which determines the   definition:     $arr 1 = Array (element 1, Element 2, ...). );     Array (1,1.1,5, ' abc ', TRUE,FALSE); Any data can be stored at this time as the default subscript     Array (2=>1,4=>1.1,3=>5,7=> ' abc ', 0=>TRUE); Subscript can be set arbitrarily (without order, without continuous)     Array (2=>1,1.1,1=>5, ' abc ', 0=>TRUE); You can add subscript, you can also not add, without subscript the default subscript                                        //default subscript rule: The maximum number that has been used before +1                 ;                        //The subscript for this number is: 2,3,1,4,0     A Rray (2=>1, ' dd ' =>5,1=>1.1, ' abc ', 0=>TRUE); Mixed subscript, also follow the default subscript rule     Array ( -2=>1, ' dd ' =>5,1.1, ' abc ', TRUE); Negative numbers are not counted in the integer subscript, but only as characters Poute                                 &NBSp        //the subscript for the last three items of this array is: 0,1,2     Array (2.7=>1, ' dd ' =>5,1=>1.1, ' abc ', TRUE); The RCAs is automatically converted to integers under floating-point numbers and directly removes the decimal part     Array ("2.7" =>1, ' DD ' =>5, "one" =>1.1, ' abc ', TRUE); A pure numeric string subscript, treated as a number     array (2=>1, ' dd ' =>5,true=>1.1, ' abc ', FALSE=>TRUE); Boolean value as Subscript, True is 1,false 0     Array (2=>1, ' dd ' =>5,2=>1.1, ' abc ', TRUE); If the subscript follows the previous repetition, it simply overwrites the target value of the preceding name       Other forms:         $arr 1[] = 1;         $arr 1[] = 5;         $arr 1[] = 1.1;         ...  //directly after the variable use [], becomes an array, and then assigns the         $arr 2[' AA '] = 1;         $arr 2[' bb '] = 5;         $arr 2[5] = 1.1;         ...  //this form of the subscript, in fact, with the array syntax structure almost the same as the category of the   array:     from the key value of the relationship is divided into:         Associative array: usually refers to the subscript as a string, and the string can generally express the meaning of the data of the array            : $person = Array ("name" => "Poe", "Age" =>, "edu" => "University Graduation");         Index array: usually refers to an array of subscript strict starting from 0 consecutive digital subscript--similar to the JS array of     from the array level:         One-dimensional array: is an array of each element value, is a normal value (not an array of values)              : $person = Array ("name" => "Poe", "a GE "=>", "edu" => "graduated from university");         Two-dimensional array: Each item in an array is a one-dimensional array.             $person = Array (                            "name" => Array ("Xiaohua", "Xiaofang),            &NBSP ;                 "age" => Array (18,22),                              "edu" => Array ("University graduate", "elementary School",)       &NBSP ;                             Multidimensional array: by analogy ...。                 General syntax form of multidimensional array:               &NBS P   $V 1 = array name [subscript] [subscript] [...]   array traversal:     TRAVERSAL basic syntax:         foreach ($arr as [$key =&G t;] $value) {           //all possible operations on the $key and $value are available here-because they are a variable       &N Bsp    //$key represents the subscript for each element, possibly a number, or it can be a string            //$value represents each time the value of the element is obtained, possibly various types            //This loop structure is traversed from the first item of the array to the last item, then the         {}   array pointer and traversal principle: &N Bsp   Each array has a "pointer" inside it that determines which element     foreach traversal is being taken when the array is currently fetched, depending on the pointer.     Example: $arr 1 = Array (2=>1, ' dd ' =>5,1=>1.1, ' abc ', 0=>TRUE);     Wkiol1znx1sxflt6aaanrltn90q498.jpg Pointers in addition to the position setting for the Foreach loop, some other functions also depend on pointers: 1: $v 1 = current ($arr 1);    //Gets the value of the element that the current pointer points to in $ARR1, or False 2: $v 1 = key ($arr 1) If there is no point to the element;        //Gets the subscript of the element that the current pointer points to in the $arr1 ... 3: $v 1 = Next ($arr 1);      //move the pointer to the next element and get the value of the next element 4: $v 1 = prev ($arr 1);      //move the pointer to the previous element and get the value of the previous element 5: $v 1 = reset ($arr 1);      //Moves the pointer to the first element and obtains the value of the element 6: $v 1 = end ($arr 1);        //moves the pointer to the last element and gets the value of the element 7: $v 1 = each ($arr 1);      //get subscript and value for the current element, then move the pointer to the next position