PHP manual Page-by-note (1)

PHP Manual Read notes (1)

1. Language Reference | Basic Syntax

? ? The end tag (?>) of the tail of the PHP file is best omitted to prevent extra spaces and carriage returns from the tail of the file

? ? You can use/*//, #方式的注释

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2. Type

? ? Supports four types of scalars: Boolean, Integer, float (same as double), string

? ? supports two types of structures: Array, object

? ? Supports three special types: resource, NULL, callable

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? ? Type does not have to be set, and PHP can derive itself from context during runtime.

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<%php$a_bool = TRUE; $a _str = "str"; $a _str2 = ' str '; $an _int = 12;echo get_type ($a _bool); if (Is_int ($an _int)) {    echo "Int";}

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? ? Boolean:true/false, (bool), empty array is also FALSE

? ? Integer: Similar to C

? ? float: similar to C

? ? String: Single quotation mark, double quotation mark (variable expandable), variable expansion in Heredoc,nowdoc,heredoc, Nowdoc not expanded, Heredoc is <<<><>< p=""><><>

? ? Array: An ordered map that can be used as an array, a linked list, a hash table, and so on. Use Array () to create a comma-separated key=>value.

???????? Key can be an integer, or it can be a string, the contents of the string is an integer, will be converted to an integer, float to an integer, a Boolean to an integer, value can be any value.

The array () structure can be replaced with [] after php5.4.

????????. PHP array key can have both integers and strings, because PHP does not differentiate between indexed arrays and associative arrays.

? ? ? ? ? ? ? ?" Key = "can be omitted, using the previous largest integer key+1,key starting from 0.

When assigning values to array members, key can also be omitted: $arr [] = 24; This is also the largest integer key+1

? ? ? ? ? ? ? Unset deleting members

? ? ? ? ? ? ? foreach Loop: foreach ($arr as $item) {$item ...}

? ? Object: An instance of a class created with new classname. Class can have method,object->xxx () access method defined by function xxx ().

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3. Variables

? ? Use $ start, case sensitive

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4. Constants

? ? Define ("name", "value");

? ? const Hello = "Hello";

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