String Variables in PHP
String variables are used for values that contain characters.
In this chapter we are going to look at the most common functions and operators used to manipulate strings in PHP. After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable. Below, the PHP script assigns the text "Hello World" to a string variable called $txt:
<?php
$txt="Hello World";
echo $txt;
?>
$txt="Hello World";
echo $txt;
?>
The output of the code above will be:
Hello World
Now, lets try to use some different functions and operators to manipulate the string.
The Concatenation Operator
There is only one string operator in PHP. The concatenation operator (.) is used to put two string values together. To concatenate two string variables together, use the concatenation operator:
<?php
$txt1="Hello World!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>
$txt1="Hello World!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>
The output of the code above will be:
Hello World! What a nice day!
If we look at the code above you see that we used the concatenation operator two times. This is because we had to insert a third string (a space character), to separate the two string
The strlen() function
The strlen() function is used to return the length of a string. Let's find the length of a string:<?php
echo strlen("Hello world!");
?>
The output of the code above will be:
12
The length of a string is often used in loops or other functions, when it is important to know when the string ends. (i.e. in a loop, we would want to stop the loop after the last character in the string).
If a match is found, this function will return the character position of the first match. If no match is found, it will return FALSE.
Let's see if we can find the string "world" in our string:
<?php
echo strpos("Hello world!","world");
?>
The output of the code above will be:
6
The position of the string "world" in the example above is 6. The reason that it is 6 (and not 7), is that the first character position in the string is 0, and not 1.
The reference contains a brief description, and examples of use, for each function!
The strpos() function
The strpos() function is used to search for a character/text within a string.If a match is found, this function will return the character position of the first match. If no match is found, it will return FALSE.
Let's see if we can find the string "world" in our string:
<?php
echo strpos("Hello world!","world");
?>
The output of the code above will be:
6
The position of the string "world" in the example above is 6. The reason that it is 6 (and not 7), is that the first character position in the string is 0, and not 1.
Complete PHP String Reference
For a complete reference of all string functions, go to our complete PHP String Reference.The reference contains a brief description, and examples of use, for each function!
PHP String Functions
PHP String Introduction
The string functions allow you to manipulate strings.Installation
The string functions are part of the PHP core. There is no installation needed to use these functions.PHP String Functions
PHP: indicates the earliest version of PHP that supports the function.| Function | Description | PHP |
|---|---|---|
| addcslashes() | Returns a string with backslashes in front of the specified characters | 4 |
| addslashes() | Returns a string with backslashes in front of predefined characters | 3 |
| bin2hex() | Converts a string of ASCII characters to hexadecimal values | 3 |
| chop() | Alias of rtrim() | 3 |
| chr() | Returns a character from a specified ASCII value | 3 |
| chunk_split() | Splits a string into a series of smaller parts | 3 |
| convert_cyr_string() | Converts a string from one Cyrillic character-set to another | 3 |
| convert_uudecode() | Decodes a uuencoded string | 5 |
| convert_uuencode() | Encodes a string using the uuencode algorithm | 5 |
| count_chars() | Returns how many times an ASCII character occurs within a string and returns the information | 4 |
| crc32() | Calculates a 32-bit CRC for a string | 4 |
| crypt() | One-way string encryption (hashing) | 3 |
| echo() | Outputs strings | 3 |
| explode() | Breaks a string into an array | 3 |
| fprintf() | Writes a formatted string to a specified output stream | 5 |
| get_html_translation_table() | Returns the translation table used by htmlspecialchars() and htmlentities() | 4 |
| hebrev() | Converts Hebrew text to visual text | 3 |
| hebrevc() | Converts Hebrew text to visual text and new lines (\n) into <br /> | 3 |
| html_entity_decode() | Converts HTML entities to characters | 4 |
| htmlentities() | Converts characters to HTML entities | 3 |
| htmlspecialchars_decode() | Converts some predefined HTML entities to characters | 5 |
| htmlspecialchars() | Converts some predefined characters to HTML entities | 3 |
| implode() | Returns a string from the elements of an array | 3 |
| join() | Alias of implode() | 3 |
| levenshtein() | Returns the Levenshtein distance between two strings | 3 |
| localeconv() | Returns locale numeric and monetary formatting information | 4 |
| ltrim() | Strips whitespace from the left side of a string | 3 |
| md5() | Calculates the MD5 hash of a string | 3 |
| md5_file() | Calculates the MD5 hash of a file | 4 |
| metaphone() | Calculates the metaphone key of a string | 4 |
| money_format() | Returns a string formatted as a currency string | 4 |
| nl_langinfo() | Returns specific local information | 4 |
| nl2br() | Inserts HTML line breaks in front of each newline in a string | 3 |
| number_format() | Formats a number with grouped thousands | 3 |
| ord() | Returns the ASCII value of the first character of a string | 3 |
| parse_str() | Parses a query string into variables | 3 |
| print() | Outputs a string | 3 |
| printf() | Outputs a formatted string | 3 |
| quoted_printable_decode() | Decodes a quoted-printable string | 3 |
| quotemeta() | Quotes meta characters | 3 |
| rtrim() | Strips whitespace from the right side of a string | 3 |
| setlocale() | Sets locale information | 3 |
| sha1() | Calculates the SHA-1 hash of a string | 4 |
| sha1_file() | Calculates the SHA-1 hash of a file | 4 |
| similar_text() | Calculates the similarity between two strings | 3 |
| soundex() | Calculates the soundex key of a string | 3 |
| sprintf() | Writes a formatted string to a variable | 3 |
| sscanf() | Parses input from a string according to a format | 4 |
| str_ireplace() | Replaces some characters in a string (case-insensitive) | 5 |
| str_pad() | Pads a string to a new length | 4 |
| str_repeat() | Repeats a string a specified number of times | 4 |
| str_replace() | Replaces some characters in a string (case-sensitive) | 3 |
| str_rot13() | Performs the ROT13 encoding on a string | 4 |
| str_shuffle() | Randomly shuffles all characters in a string | 4 |
| str_split() | Splits a string into an array | 5 |
| str_word_count() | Count the number of words in a string | 4 |
| strcasecmp() | Compares two strings (case-insensitive) | 3 |
| strchr() | Finds the first occurrence of a string inside another string (alias of strstr()) | 3 |
| strcmp() | Compares two strings (case-sensitive) | 3 |
| strcoll() | Locale based string comparison | 4 |
| strcspn() | Returns the number of characters found in a string before any part of some specified characters are found | 3 |
| strip_tags() | Strips HTML and PHP tags from a string | 3 |
| stripcslashes() | Unquotes a string quoted with addcslashes() | 4 |
| stripslashes() | Unquotes a string quoted with addslashes() | 3 |
| stripos() | Returns the position of the first occurrence of a string inside another string (case-insensitive) | 5 |
| stristr() | Finds the first occurrence of a string inside another string (case-insensitive) | 3 |
| strlen() | Returns the length of a string | 3 |
| strnatcasecmp() | Compares two strings using a "natural order" algorithm (case-insensitive) | 4 |
| strnatcmp() | Compares two strings using a "natural order" algorithm (case-sensitive) | 4 |
| strncasecmp() | String comparison of the first n characters (case-insensitive) | 4 |
| strncmp() | String comparison of the first n characters (case-sensitive) | 4 |
| strpbrk() | Searches a string for any of a set of characters | 5 |
| strpos() | Returns the position of the first occurrence of a string inside another string (case-sensitive) | 3 |
| strrchr() | Finds the last occurrence of a string inside another string | 3 |
| strrev() | Reverses a string | 3 |
| strripos() | Finds the position of the last occurrence of a string inside another string (case-insensitive) | 5 |
| strrpos() | Finds the position of the last occurrence of a string inside another string (case-sensitive) | 3 |
| strspn() | Returns the number of characters found in a string that contains only characters from a specified charlist | 3 |
| strstr() | Finds the first occurrence of a string inside another string (case-sensitive) | 3 |
| strtok() | Splits a string into smaller strings | 3 |
| strtolower() | Converts a string to lowercase letters | 3 |
| strtoupper() | Converts a string to uppercase letters | 3 |
| strtr() | Translates certain characters in a string | 3 |
| substr() | Returns a part of a string | 3 |
| substr_compare() | Compares two strings from a specified start position (binary safe and optionally case-sensitive) | 5 |
| substr_count() | Counts the number of times a substring occurs in a string | 4 |
| substr_replace() | Replaces a part of a string with another string | 4 |
| trim() | Strips whitespace from both sides of a string | 3 |
| ucfirst() | Converts the first character of a string to uppercase | 3 |
| ucwords() | Converts the first character of each word in a string to uppercase | 3 |
| vfprintf() | Writes a formatted string to a specified output stream | 5 |
| vprintf() | Outputs a formatted string | 4 |
| vsprintf() | Writes a formatted string to a variable | 4 |
| wordwrap() | Wraps a string to a given number of characters | 4 |
PHP String Constants
PHP: indicates the earliest version of PHP that supports the constant.| Constant | Description | PHP |
|---|---|---|
| CRYPT_SALT_LENGTH | Contains the length of the default encryption method for the system. For standard DES encryption, the length is 2 | |
| CRYPT_STD_DES | Set to 1 if the standard DES-based encryption with a 2 character salt is supported, 0 otherwise | |
| CRYPT_EXT_DES | Set to 1 if the extended DES-based encryption with a 9 character salt is supported, 0 otherwise | |
| CRYPT_MD5 | Set to 1 if the MD5 encryption with a 12 character salt starting with $1$ is supported, 0 otherwise | |
| CRYPT_BLOWFISH | Set to 1 if the Blowfish encryption with a 16 character salt starting with $2$ or $2a$ is supported, 0 otherwise0 | |
| HTML_SPECIALCHARS | ||
| HTML_ENTITIES | ||
| ENT_COMPAT | ||
| ENT_QUOTES | ||
| ENT_NOQUOTES | ||
| CHAR_MAX | ||
| LC_CTYPE | ||
| LC_NUMERIC | ||
| LC_TIME | ||
| LC_COLLATE | ||
| LC_MONETARY | ||
| LC_ALL | ||
| LC_MESSAGES | ||
| STR_PAD_LEFT | ||
| STR_PAD_RIGHT | ||
| STR_PAD_BOTH |
http://www.w3schools.com/php/php_string.asp
No comments:
Post a Comment