1. Chapter 3 Manipulating Strings PHP Programming with MySQL 2nd Edition Modified by Anita Philipp –Spring 2011

2. PHP Programming with MySQL, 2nd Edition
Objectives
In this chapter, you will:
Construct text strings
Work with single strings
Work with multiple strings and parse strings
Compare strings
Use regular expressions
PHP Programming with MySQL, 2nd Edition

3. Constructing Text Strings
A text string contains zero or more characters surrounded by double or single quotation marks
Text can be used as literals or be assigned to variables
echo "<p>PHP literal text string</p>";
$TextString =‘<p>PHP text string</p>’; echo $TextString
Strings must begin and end with matching quotation marks
PHP Programming with MySQL, 2nd Edition

4. Constructing Text Strings (continued)
Alternate single and double quotes $Quote='<p>"Et tu, Brute!"</p>'; echo $Quote;
PHP Programming with MySQL, 2nd Edition

5. Working with String Operators
Concatenation operator (.) combines two strings and assigns the new value to a variable
$City = “Paris”;
$Country = “France”;
$Place = “<p>” . $City . “, “ . $Country . “</p>”;
echo $Place;
PHP Programming with MySQL, 2nd Edition

6. Working with String Operators
Combine strings using the concatenation assignment operator (.=)
$Destination = "<p>Paris";
$Destination .= ” is in France.</p>";
echo $Destination;
PHP Programming with MySQL, 2nd Edition

7. PHP Programming with MySQL, 2nd Edition
Escape Characters
Escape Character
Character that follows it has a special purpose
Escape character is the backslash (\)
echo '<p>This code\'s going to work</p>';
Not needed if single/double quotes are alternated
echo "<p>This code's going to work.</p>";
PHP Programming with MySQL, 2nd Edition

8. PHP Programming with MySQL, 2nd Edition
Escape Sequence
Escape character combined with one or more other characters
PHP Programming with MySQL, 2nd Edition

9. PHP Programming with MySQL, 2nd Edition
Escape Sequences
$Speaker = "Julius Caesar”; echo "<p>\"Et tu, Brute!\" exclaimed $Speaker.</p>";
PHP Programming with MySQL, 2nd Edition

10. Simple / Complex String Syntax
Simple string syntax
Include variable name inside a string with double quotes
$Vegetable = "broccoli";
echo "<p>Do you have any $Vegetable?</p>”;
Complex string syntax
Variables are within curly braces inside of a string
$Vegetable = "carrot";
echo "<p>Do you have any {$Vegetable}s?</p>";
PHP Programming with MySQL, 2nd Edition

11. String Functions: strlen()
returns the number of characters in a string
Escape sequences, such as \n, are counted as one character
$TextString = 'Cody\'s Car';
$TextLength = strlen($TextString);
echo "<p>$TextString contains $TextLength characters.</p>";
PHP Programming with MySQL, 2nd Edition

12. String Functions: str_word_count()
Pass a literal string or a string variable
Returns the number of words in a string
$String = 'Cody\'s Car';
$Words = str_word_count($String);
echo "<p>$String contains $Words words.</p>";
PHP Programming with MySQL, 2nd Edition

13. String Functions: Change Case
strtoupper() converts all letters to uppercase
strtolower() converts all letters to lowercase
ucfirst()ensures the first character is uppercase
lcfirst()ensures the first character is lowercase (PHP 5.3+)
ucwords()ensures all words begin with uppercase
$String = "look at me”; echo"<p>";
echo strtoupper($String)."<br/>";
echo strtolower($String)."<br/>";
echo ucfirst($String)."<br/>";
echo lcfirst($String)."<br/>";
echo ucwords($String); echo "</p>";
PHP Programming with MySQL, 2nd Edition

14. String Functions: Encode/Decode
htmlspecialchars()
converts special chars to HTML entities
html_specialcharacters_decode()
converts HTML entities into their equivalent chars
$new = htmlspecialchars("Encode: \” <hr/>");
echo ”<p>$new</p>";
$str = 'Decode: " <br/>';
echo ”<p>”.htmlspecialchars_decode($str). ”</p>”;
PHP Programming with MySQL, 2nd Edition

15. String Functions: Encode/Decode
htmlspecialchars()conversions:
&  &
“  "1.
’  '2.
<  <
>  >
ENT_NOQUOTES - disables conversion of “
ENT_QUOTES - enables conversion of ‘
PHP Programming with MySQL, 2nd Edition

16. String Functions: Encode/Decode
md5()
Creates a one-way hash*
Utilizes strong encryption algorithm
Message-Digest Algorithm
No equivalent decode function – useful for storing passwords
$Password = "str0ngpwd"; $HashResult = md5($Password); echo $HashResult;
*one-way hash is a fixed-length string based on the entered text, from which it is nearly impossible to determine the original text
PHP Programming with MySQL, 2nd Edition

17. String Functions: trim()
trim() removes leading and trailing spaces
ltrim()removes only leading spaces
rtrim()removes only the trailing spaces
$String = " spaces ”;
echo "<p>trim() |” . trim($String) . "|</p>";
echo"<p>ltrim() |” . ltrim($String) . "|</p>";
echo "<p>rtrim() |” . rtrim($String) . "|</p>";
PHP Programming with MySQL, 2nd Edition

18. String Functions: substr()
Returns substring using parameters of start and length
Start Parameter
Positive - start position from beginning (begins with 0)
Negative - start position from end
0 – start position is the beginning
Length Parameter
Default – to end of string
Positive – length from start parameter
Negative – number of characters omitted from the end of the string
Greater than remaining characters – remaining string returned
PHP Programming with MySQL, 2nd Edition

19. String Functions: substr()
$ExampleString = "woodworking project”; echo "1 ". substr($ExampleString,4) . "<br />”; echo "2 ". substr($ExampleString,4,7). "<br />”; echo "3 ". substr($ExampleString,0,8). "<br />”; echo "4 ". substr($ExampleString,4,-8)."<br />”; echo "5 ". substr($ExampleString,-7) . "<br />”; echo "6 ". substr($ExampleString,-15,4). "<br />”; echo "7 ". substr($ExampleString,-15,-8). "<br />";
PHP Programming with MySQL, 2nd Edition

20. String Functions: Parsing
Dividing a string into substrings / tokens
String search and extraction functions
Return a numeric position in a text string …or…
Return a character or substring …or…
Return FALSE if not found
PHP Programming with MySQL, 2nd Edition

21. String Functions: strpos()
case-sensitive search
returns the position of first occurrence of string
returns FALSE if not found
stripos()
case-insensitive search
Two arguments: string to be searched, characters for which to search
$String =
$Result =
echo "Result: $Result <br />";
$Result = strpos("$String”,”A");
echo "CaseSensitive: $Result <br />”;
$Result = stripos("$String”,”A");
echo "Case Insensitive: $Result <br />"
PHP Programming with MySQL, 2nd Edition

22. String Functions: strchr()
strchr(), strrchr()
Arguments: string, search character
return a substring from the specified characters to the end of the string
strchr() search from beginning
strrchr() search from end
$String="Red Rover";
echo "Beginning: ”.strchr($String,"R").”<br />";
echo "End: ”.strrchr($String,"R”).”<br />";
echo "Beginning: ”.strchr($String,"r").”<br />";
echo "End: ”.strrchr($String, "r").”<br />";
PHP Programming with MySQL, 2nd Edition

23. String Functions: strreplace()
str_replace(), str_ireplace()
Arguments: search string, replacement string, string
str_replace()– case sensitive
str_ireplace()– case insensitive
$ =
$Search = "mr.president";
$New = str_replace($Search,"Mr.Vice.President”,$ );
echo $New ."<br/>";
$New = str_ireplace($Search,"Mr.Vice.President”,$ );
echo $New ;
PHP Programming with MySQL, 2nd Edition

24. String Functions: strtok()
strtok() divide a string into tokens
Arguments: String, separator
Returns entire string when
An empty string is specified as the second argument
Does not contain any of the separators
$Presidents = "Washington|Jefferson|Madison";
$MrPresident = strtok($Presidents, ”|");
while ($MrPresident != NULL) {
echo "$MrPresident<br />";
$MrPresident = strtok(";"); }
PHP Programming with MySQL, 2nd Edition

25. String Functions: str_split(), explode()
str_split(), explode() split a string into an indexed array
str_split()
Arguments: string, length of each element
explode()
Arguments: separators, string
When separators not found, entire string is assigned to $ArrayName[0]
Does not separate a string at each character that is included in the separator argument
Evaluates the characters in the separator argument as a substring
Empty string as the separator argument then function returns a Boolean value of FALSE
PHP Programming with MySQL, 2nd Edition

26. String Functions: str_split(), explode()
$States = "Oklahoma;Texas"; $StatesArray = explode(";", $States); foreach ($StatesArray as $StateCode) { echo "$StateCode<br />"; } $States = "OKTX"; $StatesArray = str_split($States, 2);
PHP Programming with MySQL, 2nd Edition

27. String Functions: implode()
combines an array’s elements into a single string
separated by specified characters
Arguments: separators, array
$DaysArray = array("FR","SA","SU");
$Weekend = implode(", ",$DaysArray);
echo "$Weekend";
PHP Programming with MySQL, 2nd Edition

28. String Functions: Comparisons
Comparison operators use ASCII codes
Lowercase letters
97 (“a”) to 122 (“z”)
Uppercase letters
65 (“A”) to 90 (“Z”)
$First = "A"; $Second = "a";
if ($First > $Second )
echo "<p>$First is greater than $Second./p>";
else
echo "<p>$Second is greater than $First.</p>";
PHP Programming with MySQL, 2nd Edition

29. String Functions: Comparisons
strcasecmp(), strcmp()
Arguments: String 1, String 2
Compare based on ASCII Value
Positive number – first is greater
Negative number - second is greater
strcasecmp() – case-insensitive
strcmp() – case-sensitive
strncmp(), strncasecmp()
Arguments: String 1, String 2, Number of chars to compare
Similar strings – longer is greater
$First = "Birth”;
$Second = "Birthday";
echo ”Result strcmp: ". strcmp($First, $Second)."<br/>”;
echo ”Result strncmp: ". strncmp($First, $Second, 5);
PHP Programming with MySQL, 2nd Edition

30. String Functions: Similar Text
similar_text() , levenshtein()
Determine similarity between two strings
Arguments: two strings
similar_text()
returns the number of common characters
levenshtein()
returns the number of characters needing change to make strings the same
$First = "Smith";
$Second = "Smyth";
$Same = similar_text($First, $Second);
$Change = levenshtein($First, $Second);
echo"<p>$First|$Second have $Same chars in common.</p>";
echo"<p>$First|$Second have $Change chars to change.</p>";
PHP Programming with MySQL, 2nd Edition

31. String Functions: Sound Comparisons
soundex(), metaphone()
Can use to determine whether strings are pronounced similarly
Return a value representing how words sound
soundex()
Returns 4 character alphanumeric representing pronunciations (English)
metaphone()
Returns code representing word’s approximate sound (English)
$First = "son"; $Second = "sun";
$Soundex1=soundex($First); $Soundex2=soundex($Second);
$MPhone1=metaphone($First); $MPhone2=metaphone($Second);
echo "For son and sun:<br/>";
echo "soundex codes: $Soundex1 and $Soundex2<br/>";
echo "metaphone codes: $MPhone1 and $MPhone2";
PHP Programming with MySQL, 2nd Edition

32. THE
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