Php manual reading notes (1)

Php manual reading notes (1) 1. using agereference | BasicSyntax ?? End mark at the end of the PHP file (? & Gt;) it is best to omit it to prevent unnecessary spaces and carriage return characters from being added to the end of the file ?? Can I use/**/, //, # comment? 2. type ?? Php manual reading notes (1)

1. Language Reference | Basic Syntax

? ? End mark at the end of the PHP file (?>) It is best to omit it to prevent unnecessary spaces and carriage returns from being added to the end of the file.

? ? You can use/**/, //, # annotations.

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2. type

? ? Four scalar types are supported: boolean, integer, float (same as double), string

? ? Two structures are supported: array and object.

? ? Three special types are supported: resource, NULL, and callable.

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? ? You do not need to set the type. during The runtime, PHP can be derived based on the context.

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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 marks, double quotation marks (variable extensible), variables in heredoc, nowdoc, and heredoc are expanded. variables in nowdoc are not expanded. heredoc is <

? ? Array: an ordered map, which can be used as an array, a linked list, or a hash table. Create With array (), where key => value can be separated by commas.

? ? ? ? ? ? ? ? The key can be an integer or a string. if the content in the string is an integer, it will be converted to an integer; float can be converted to an integer, boolean can be converted to an integer, and value can be any value.

? ? ? ? ? ? ? ? After php5.4, the array () structure can be replaced with [].

? ? ? ? ? ? ? ? Php array keys can have both integers and strings, because php does not distinguish between index arrays and associated arrays.

? ? ? ? ? ? ? ? "Key =>" can be omitted. the preceding largest integer key + 1 is used, and the key starts from 0.

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

? ? ? ? ? ? ? Unset

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

? ? Object: A class instance created through the new classname. Class can have function xxx () defined method, object-> xxx () access method.

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3. variables

? ? Starts with $ and is case sensitive.

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4. constants

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

? ? Const HELLO = "hello ";

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