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Objectives

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

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Objectives

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  1. Chapter 3Manipulating StringsPHP Programming with MySQL2nd EditionModified by Anita Philipp –Spring 2011

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

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

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

  11. String Functions: strlen() • 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() • 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>"; $str = 'Decode: &quot; &lt;br/&gt;'; echo ”<p>”.htmlspecialchars_decode($str).”</p>”; PHP Programming with MySQL, 2nd Edition

  15. String Functions: Encode/Decode • htmlspecialchars()conversions: • &&amp; • “ &quot;1. • ’&#039;2. • <&lt; • >&gt; • 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() $String = " spaces ”; echo "<p>trim() |” . trim($String) . "|</p>"; echo"<p>ltrim() |” . ltrim($String) . "|</p>"; echo "<p>rtrim() |” . rtrim($String) . "|</p>"; • trim()removes leading and trailing spaces • ltrim()removes only leading spaces • rtrim()removes only the trailing spaces PHP Programming with MySQL, 2nd Edition

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

  22. String Functions: strchr() $String="Red Rover"; echo "Beginning: ”.strchr($String,"R").”<br />"; echo "End: ”.strrchr($String,"R”).”<br />"; echo "Beginning: ”.strchr($String,"r").”<br />"; echo "End: ”.strrchr($String, "r").”<br />"; • 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 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 $Email = "Mr.President@whitehouse.gov"; $Search = "mr.president"; $NewEmail = str_replace($Search,"Mr.Vice.President”,$Email); echo $NewEmail."<br/>"; $NewEmail = str_ireplace($Search,"Mr.Vice.President”,$Email); echo $NewEmail; 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); foreach ($StatesArray as $StateCode) { echo "$StateCode<br />"; } PHP Programming with MySQL, 2nd Edition

  27. String Functions: implode() • 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 END

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