Variables In Php Start With
What are the rules for naming variables in PHP?Rules for PHP variables: 1 A variable starts with the $ sign, followed by the name of the variable 2 A variable name must start with a letter or the underscore character 3 A variable name cannot start with a number 4 A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ) More items PHP Variables — W3Schools
Value of abc : Welcome Value of ABC : '; echo $foo; ?> my bob my bob "; echo "The value of y is : $y"."
"; > var_scope(); echo "The value of x is : $x"."
"; echo "The value of y is : $y "; ?> The value of x is : The value of y is : 20 The value of x is : 10 The value of y is : multiple(); echo $xyz; ?> test_variable(); echo "
"; test_variable(); echo "
"; test_variable(); ?> 1 1 1 test_count(); echo "
"; test_count(); echo "
"; test_count(); ?> 1 2 3 return number_format((float)$number, 2, '.', ''); $foo = "105"; echo number_format((float)$foo, 2, '.', ''); // Outputs -> 105.00Variables in PHP
The following article, variables in PHP, provides an outline for the various variables available in PHP. Each variable stores some kind of …
$5input = 'Demo'; $_input = 'Demo'; $input = 'Demo'; $_5input = 'Demo'; '; var_dump($y); ?> $input is my favorite fruit'; echo "
$input is my favorite fruit"; ?> True is ".$input; $input_value = false; // print false echo "
False is ".$input_value; ?> '; var_dump($input_value); ?> string; > > //instantiating an object of a class $object = new Subject; echo $object->string; ?> '; echo $directions[2] echo '
'; echo $directions[0]; ?> '; $input = NULL; var_dump($input); ?> PHP variables
Variable is a symbol or name that stands for a value. Variables are used for storing values such as numeric values, characters, character …
Value of abc : Welcome Value of ABC : '; echo $foo; ?> my bob my bob "; echo "The value of y is : $y"."
"; > var_scope(); echo "The value of x is : $x"."
"; echo "The value of y is : $y "; ?> The value of x is : The value of y is : 20 The value of x is : 10 The value of y is : multiple(); echo $xyz; ?> test_variable(); echo "
"; test_variable(); echo "
"; test_variable(); ?> 1 1 1 test_count(); echo "
"; test_count(); echo "
"; test_count(); ?> 1 2 3 return number_format((float)$number, 2, '.', ''); $foo = "105"; echo number_format((float)$foo, 2, '.', ''); // Outputs -> 105.00PHP Variables
If you declare a variable in PHP, that means you are asking to the operating system of web server for reserve a piece of memory with that variable name. Variable Definition and …
$funct = "testFunction"; $funct(); // will call testFunction(); ?>Why PHP variables start with a $ sign symbol?
46. Because PHP was based on Perl which used $, though the symbols Perl used were meaningful and plenty used to indicate the data type, ( such as @ used to indicate an …
10 PRINT "WHAT IS YOUR NAME?" 20 INPUT A$ 30 IF A$="BAHKTIYOR" THEN PRINT "HEY CHECK OUT THAT DOLLAR SIGN"str_starts_with
Performs a case-sensitive check indicating if haystack begins with needle .
Parameters
The substring to search for in the haystack .
Return Values
Returns true if haystack begins with needle , false otherwise.
Examples
Example #1 Using the empty string »
The above example will output:
All strings start with the empty string
Example #2 Showing case-sensitivity
$string = ‘The lazy fox jumped over the fence’ ;
if ( str_starts_with ( $string , ‘The’ )) echo «The string starts with ‘The’\n» ;
>
if ( str_starts_with ( $string , ‘the’ )) echo ‘The string starts with «the»‘ ;
> else echo ‘»the» was not found because the case does not match’ ;
>
The above example will output:
The string starts with 'The' "the" was not found because the case does not match
Notes
Note: This function is binary-safe.
See Also
- str_contains() — Determine if a string contains a given substring
- str_ends_with() — Checks if a string ends with a given substring
- stripos() — Find the position of the first occurrence of a case-insensitive substring in a string
- strrpos() — Find the position of the last occurrence of a substring in a string
- strripos() — Find the position of the last occurrence of a case-insensitive substring in a string
- strstr() — Find the first occurrence of a string
- strpbrk() — Search a string for any of a set of characters
- substr() — Return part of a string
- preg_match() — Perform a regular expression match
User Contributed Notes 2 notes
With credit to Paul Phillips for the original polyfill posted.
If you do not have PHP 8, you can use these functions to get the capability of the new string functions.
But! Remember to use a conditional check to make sure the function is not already defined.
// source: Laravel Framework
// https://github.com/laravel/framework/blob/8.x/src/Illuminate/Support/Str.php
if (! function_exists ( ‘str_starts_with’ )) function str_starts_with ( $haystack , $needle ) return (string) $needle !== » && strncmp ( $haystack , $needle , strlen ( $needle )) === 0 ;
>
>
if (! function_exists ( ‘str_ends_with’ )) function str_ends_with ( $haystack , $needle ) return $needle !== » && substr ( $haystack , — strlen ( $needle )) === (string) $needle ;
>
>
if (! function_exists ( ‘str_contains’ )) function str_contains ( $haystack , $needle ) return $needle !== » && mb_strpos ( $haystack , $needle ) !== false ;
>
>
?>
This keeps it from breaking in case you upgrade and forget that you added it. This is a good practice generally when using the global scope for your helper functions.
In PHP7 you may want to use:
if (!function_exists(‘str_starts_with’)) function str_starts_with($str, $start) return (@substr_compare($str, $start, 0, strlen($start))==0);
>
>
AFAIK that is binary safe and doesn’t need additional checks.
Php variable start with
Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive.
Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: ^[a-zA-Z_\x80-\xff][a-zA-Z0-9_\x80-\xff]*$
Note: For our purposes here, a letter is a-z, A-Z, and the bytes from 128 through 255 ( 0x80-0xff ).
Note: $this is a special variable that can’t be assigned. Prior to PHP 7.1.0, indirect assignment (e.g. by using variable variables) was possible.
For information on variable related functions, see the Variable Functions Reference.
$var = ‘Bob’ ;
$Var = ‘Joe’ ;
echo » $var , $Var » ; // outputs «Bob, Joe»
$ 4site = ‘not yet’ ; // invalid; starts with a number
$_4site = ‘not yet’ ; // valid; starts with an underscore
$täyte = ‘mansikka’ ; // valid; ‘ä’ is (Extended) ASCII 228.
?>
By default, variables are always assigned by value. That is to say, when you assign an expression to a variable, the entire value of the original expression is copied into the destination variable. This means, for instance, that after assigning one variable’s value to another, changing one of those variables will have no effect on the other. For more information on this kind of assignment, see the chapter on Expressions.
PHP also offers another way to assign values to variables: assign by reference. This means that the new variable simply references (in other words, «becomes an alias for» or «points to») the original variable. Changes to the new variable affect the original, and vice versa.
To assign by reference, simply prepend an ampersand (&) to the beginning of the variable which is being assigned (the source variable). For instance, the following code snippet outputs ‘ My name is Bob ‘ twice:
$foo = ‘Bob’ ; // Assign the value ‘Bob’ to $foo
$bar = & $foo ; // Reference $foo via $bar.
$bar = «My name is $bar » ; // Alter $bar.
echo $bar ;
echo $foo ; // $foo is altered too.
?>
One important thing to note is that only named variables may be assigned by reference.
$foo = 25 ;
$bar = & $foo ; // This is a valid assignment.
$bar = &( 24 * 7 ); // Invalid; references an unnamed expression.
It is not necessary to initialize variables in PHP however it is a very good practice. Uninitialized variables have a default value of their type depending on the context in which they are used — booleans default to false , integers and floats default to zero, strings (e.g. used in echo ) are set as an empty string and arrays become to an empty array.
Example #1 Default values of uninitialized variables
// Unset AND unreferenced (no use context) variable; outputs NULL
var_dump ( $unset_var );
// Boolean usage; outputs ‘false’ (See ternary operators for more on this syntax)
echo $unset_bool ? «true\n» : «false\n» ;
// String usage; outputs ‘string(3) «abc»‘
$unset_str .= ‘abc’ ;
var_dump ( $unset_str );
// Integer usage; outputs ‘int(25)’
$unset_int += 25 ; // 0 + 25 => 25
var_dump ( $unset_int );
// Float usage; outputs ‘float(1.25)’
$unset_float += 1.25 ;
var_dump ( $unset_float );
// Array usage; outputs array(1) < [3]=>string(3) «def» >
$unset_arr [ 3 ] = «def» ; // array() + array(3 => «def») => array(3 => «def»)
var_dump ( $unset_arr );
// Object usage; creates new stdClass object (see http://www.php.net/manual/en/reserved.classes.php)
// Outputs: object(stdClass)#1 (1) < ["foo"]=>string(3) «bar» >
$unset_obj -> foo = ‘bar’ ;
var_dump ( $unset_obj );
?>
Relying on the default value of an uninitialized variable is problematic in the case of including one file into another which uses the same variable name. E_WARNING (prior to PHP 8.0.0, E_NOTICE ) level error is issued in case of working with uninitialized variables, however not in the case of appending elements to the uninitialized array. isset() language construct can be used to detect if a variable has been already initialized.
User Contributed Notes 5 notes
This page should include a note on variable lifecycle:
Before a variable is used, it has no existence. It is unset. It is possible to check if a variable doesn’t exist by using isset(). This returns true provided the variable exists and isn’t set to null. With the exception of null, the value a variable holds plays no part in determining whether a variable is set.
Setting an existing variable to null is a way of unsetting a variable. Another way is variables may be destroyed by using the unset() construct.
print isset( $a ); // $a is not set. Prints false. (Or more accurately prints ».)
$b = 0 ; // isset($b) returns true (or more accurately ‘1’)
$c = array(); // isset($c) returns true
$b = null ; // Now isset($b) returns false;
unset( $c ); // Now isset($c) returns false;
?>
is_null() is an equivalent test to checking that isset() is false.
The first time that a variable is used in a scope, it’s automatically created. After this isset is true. At the point at which it is created it also receives a type according to the context.
$a_bool = true ; // a boolean
$a_str = ‘foo’ ; // a string
?>
If it is used without having been given a value then it is uninitalized and it receives the default value for the type. The default values are the _empty_ values. E.g Booleans default to FALSE, integers and floats default to zero, strings to the empty string », arrays to the empty array.
A variable can be tested for emptiness using empty();
$a = 0 ; //This isset, but is empty
?>
Unset variables are also empty.
empty( $vessel ); // returns true. Also $vessel is unset.
?>
Everything above applies to array elements too.
$item = array();
//Now isset($item) returns true. But isset($item[‘unicorn’]) is false.
//empty($item) is true, and so is empty($item[‘unicorn’]
$item [ ‘unicorn’ ] = » ;
//Now isset($item[‘unicorn’]) is true. And empty($item) is false.
//But empty($item[‘unicorn’]) is still true;
$item [ ‘unicorn’ ] = ‘Pink unicorn’ ;
//isset($item[‘unicorn’]) is still true. And empty($item) is still false.
//But now empty($item[‘unicorn’]) is false;
?>
For arrays, this is important because accessing a non-existent array item can trigger errors; you may want to test arrays and array items for existence with isset before using them.