Working with Variables


Using variables in PHP is nearly as easy as using them in JavaScript. In PHP, variables can store numbers, strings, or objects, just as they can in JavaScript. Unlike JavaScript, however, variables names start with $ in PHP, and you don’t need to declare them, as with the var statement in JavaScript.

For example, here is how you set the variable named $sandwiches to 1:

 $sandwiches = 1;

And here is how you can display the value in this variable with the echo statement:

 echo "Number of sandwiches: ", $sandwiches, "<br>";

Note 

You can pass multiple items to the echo statement if you separate them with commas. Also, you’re echoing HTML to the browser here, so that can include HTML elements like <br>.

Here’s an example, variables.php, that puts variables to work. This example starts by assigning the variable $sandwiches a value of 2:

 <html>     <head>         <title>             Using variables         </title>     </head>     <body>         <h1>            Using variables         </h1>         <?             echo "Setting number of sandwiches to 2.<br>";             $sandwiches = 2;             .             .             .         ?>     </body> </html>

and it echoes the number of sandwiches to the browser:

 <html>         .         .         .         <?            echo "Setting number of sandwiches to 2.<br>";            $sandwiches = 2;            echo "Number of sandwiches: ", $sandwiches, "<br>";            .            .            .        ?>     </body> </html>

Then the code adds two more sandwiches to the total, using the PHP + operator, which acts just like the JavaScript + operator:

 <html>         .         .         .         <?            echo "Setting number of sandwiches to 2.<br>";            $sandwiches = 2;            echo "Number of sandwiches: ", $sandwiches, "<br>";            echo "Adding 2 more sandwiches.<BR>";              $sandwiches = $sandwiches + 2;            .            .            .         ?>     </body> </html>

and then the code displays the new number of sandwiches:

 <html>         .         .         .         <?            echo "Setting number of sandwiches to 2.<br>";            $sandwiches = 2;            echo "Number of sandwiches: ", $sandwiches, "<br>";            echo "Adding 2 more sandwiches.<BR>";            $sandwiches = $sandwiches + 2;            echo "Number of sandwiches now: ", $sandwiches, "<br>";         ?>     </body> </html>

You can see the results in Figure 12.4.

image from book
Figure 12.4: Using variables

In addition to assigning numbers to variables, you can also assign text strings, as shown here:

 $string = "Hello from PHP.";

In JavaScript, you join strings with the + operator, but in PHP, you use the dot (.) operator instead:

 $string = "Hello " . "from " . "PHP.";

For more string power, PHP comes with many string functions built in:

  • The trim function trims spaces from the beginning and end of a string.

  • The substr function extracts substrings from a string.

  • The strpos function finds the location of a substring in a string.

  • The substr_replace function replaces text in a string.

  • The strtoupper function converts a whole string to uppercase.

The example, string.php, puts these string functions to work. It starts by trimming the extra white space off the string " I like PHP." with the trim function:

 <html>     <head>         <title>             Using strings         </title>     </head>     <body>         <h1>             Using strings         </h1>         <?           echo trim("        I like PHP."), "<br>";           .           .           .         ?>     </body> </html>

then it uses the substr function to extract the text PHP from the string "I like PHP.":

 <html>     <head>         <title>             Using strings         </title>     </head>     <body>         <h1>             Using strings         </h1>         <?           echo trim("I like PHP."), "<br>";           echo substr("I like PHP.", 7, 3), "<br>";           .           .           .         ?>     </body> </html>

The code then uses the strpos function to locate the first occurrence of PHP in the text "I like PHP." like this:

 <html>         .         .         .         <?           echo trim("      I like PHP."), "<br>";           echo substr("I like PHP.", 7, 3), "<br>";           echo "'PHP' starts at position ", strpos("I like PHP.",             "PHP"), "<br>";           .           .           .         ?>     </body> </html>

and then the code determines how long the string "I like PHP." is:

 <html>         .         .         .         <?           echo trim("      I like PHP."), "<br>";           echo substr("I like PHP.", 7, 3), "<br>";           echo "'PHP' starts at position ", strpos("I like PHP.",             "PHP"), "<br>";           echo "'I like PHP.' is ", strlen("I like PHP."),             " characters long.<br>";           .           .           .         ?>     </body> </html>

This example also replaces like in "I like PHP." with love using substr_replace:

 <html>         .         .         .         <?           echo trim("      I like PHP."), "<br>";           echo substr("I like PHP.", 7, 3), "<br>";           echo "'PHP' starts at position ", strpos("I like PHP.",             "PHP"), "<br>";           echo "'I like PHP.' is ", strlen("I like PHP."),             " characters long.<br>";           echo substr_replace("I like PHP.", "love", 2, 4),             "<br>";           .           .           .         ?>     </body> </html>

and the example winds down by converting "I like PHP." to uppercase with strtoupper:

 <html>         .         .         .         <?           echo trim("     I like PHP."), "<br>";           echo substr("I like PHP.", 7, 3), "<br>";           echo "'PHP' starts at position ", strpos("I like PHP.",             "PHP"), "<br>";           echo "'I like PHP.' is ", strlen("I like PHP."),             " characters long.<br>";           echo substr_replace("I like PHP.", "love", 2, 4),             "<br>";           echo strtoupper("I like PHP."), "<br>";         ?>     </body> </html>

You can see the results in Figure 12.5.

image from book
Figure 12.5: Using string functions

Table 12.1 lists all the PHP string functions and what they do.

Table 12.1: The String Functions
Open table as spreadsheet

Function

Does This

addslashes

Quotes a string with slashes

bin2hex

Converts binary data into hexadecimal representation

chop

Alias of the trim function

chr

Returns a specific character given its ASCII code

chunk_split

Splits a string into smaller chunks

convert_cyr_string

Converts from one Cyrillic character set to another

count_chars

Returns information about characters in a string

crc32

Calculates the crc32 polynomial of a string

crypt

Supports one-way string encryption (hashing)

echo

Displays one or more strings

explode

Splits a string on a substring

fprintf

Writes a formatted string to a stream

get_html_translation_table

Returns the translation table

hebrev

Converts Hebrew text to visual text

hebrevc

Converts logical Hebrew text to visual text

html_entity_decode

Converts all HTML entities to their applicable characters

htmlentities

Converts all applicable characters to HTML entities

htmlspecialchars

Converts special characters to HTML entities

implode

Joins array elements with a string

join

Alias of the implode function

levenshtein

Calculates the Levenshtein distance between two strings

localeconv

Gets the numeric formatting information

ltrim

Strips white space from the beginning of a string

md5_file

Calculates the md5 hash of a given filename

md5

Calculates the md5 hash of a string

metaphone

Calculates the metaphone key of a string

money_format

Formats a number as a currency string

nl_langinfo

Queries language and locale information

nl2br

Inserts HTML line breaks before all new lines in a string

number_format

Formats a number with grouped thousand separators

ord

Returns the ASCII value of character

parse_str

Parses the string into variables

print

Displays a string

printf

Displays a formatted string

quoted_printable_decode

Converts a quoted-printable string to an 8-bit string

quotemeta

Quotes meta characters

rtrim

Strips white space from the end of a string

setlocale

Sets locale information

sha1_file

Calculates the sha1 hash of a file

sha1

Calculates the sha1 hash of a string

similar_text

Calculates the similarity between two strings

soundex

Calculates the soundex key of a string

sprintf

Returns a formatted string

sscanf

Parses input from a string according to a format

str_ireplace

Case-insensitive version of the str_replace function

str_pad

Pads a string with another string

str_repeat

Repeats a string

str_replace

Replaces all occurrences of the search string with the replacement string

str_rot13

Performs the rot13 transform on a string

str_shuffle

Shuffles a string randomly

str_split

Converts a string to an array

str_word_count

Returns information about words used in a string

strcasecmp

Binary case-insensitive string comparison

strchr

Alias of the strstr function

strcmp

Binary-safe string comparison

strcoll

Locale-based string comparison

strcspn

Finds the length of the initial segment not matching a mask

strip_tags

Strips HTML and PHP tags from a string

stripcslashes

Un-quotes string quoted with addcslashes()

stripos

Finds position of first occurrence of a case-insensitive string

stripslashes

Un-quotes string quoted with addslashes()

stristr

Case-insensitive version of the strstr function

strlen

Gets a string’s length

strnatcasecmp

Case-insensitive string comparisons

strnatcmp

String comparisons using a “natural order” algorithm

strncasecmp

Binary case-insensitive string comparison of the first n characters

strncmp

Binary safe string comparison of the first n characters

strpos

Finds position of first occurrence of a string

strrchr

Finds the last occurrence of a character in a string

strrev

Reverses a string

strripos

Finds the position of last occurrence of a case-insensitive string

strrpos

Finds the position of last occurrence of a char in a string

strspn

Finds the length of initial segment matching mask

strstr

Finds the first occurrence of a string

strtok

Tokenizes a string

strtolower

Converts a string to lowercase

strtoupper

Converts a string to uppercase

strtr

Translates certain characters

substr_compare

Binary-safe (optionally case-insensitive) comparison of 2 strings from an offset

substr_count

Counts the number of substring occurrences

substr_replace

Replaces text within part of a string

substr

Returns part of a string

trim

Strips white space from the beginning and end of a string

ucfirst

Makes a string’s first character uppercase

ucwords

Uppercases the first character of each word in a string

vprintf

Outputs a formatted string

vsprintf

Returns a formatted string

wordwrap

Wraps a string to a given number of characters



Ajax Bible
Ajax Bible
ISBN: 0470102632
EAN: 2147483647
Year: 2004
Pages: 169

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