MCIS/UA PHP Training 2003 Chapter 6 Strings
String Literals • Single-quoted strings • Double-quoted strings escape sequences
String Literals Interpreted items Single-quoted Double-quoted \' - single quote variables - value of variable \\ - backslash \n - new line \r - return \t - tab \\ - backslash \$ - dollar sign \" - double quote \ nnn - ASCII char in octal \x nn - ASCII char in hex heredoc
Here Documents • The <<< operator (also known as heredoc) can be used to construct multi-line strings. $myString = <<< End This is a multi-line string. This is the second line. This is the third line. End; print $myString; This is a multi-line string. This is the second line. This is the third line. →
Here Documents $name = $info->queryFirstColumn( "SELECT name ". "FROM info ". "WHERE uniqueid = ?", $uid); $sql = <<< end_of_sql SELECT name FROM info WHERE uniqueid = ? end_of_sql; $name = $info->queryFirstColumn($sql, $uid); →
Here Documents $name = $info->queryFirstColumn(<<< end_of_sql SELECT name FROM info WHERE uniqueid = ? end_of_sql , $uid); outputting
Outputting strings • Several ways to output strings and other data: echo print printf sprintf print_r var_dump echo and print
echo and print • echo and print output data and are pretty much identical $x = "abc"; echo "value: $x"; → value: abc print "value: $x"; → value: abc printf
printf • printf outputs formatted data $x = 5; printf("value: %d", $x); → value: 5 $mon = 4; $day = 8; $year = 2003; printf("%d/%d/%d", $mon, $day, $year); 4/8/2003 format codes
printf Format Codes format result input output %% percent sign % %d integer -123.45 -123 %f floating point -123.45 -123.450000 %s string abc abc %b binary 5 101 %c character 65 A %o octal 255 377 %x hex (lowercase) 123456789 75bcd15 %X hex (uppercase) 123456789 75BCD15 %u unsigned integer -123.45 4294967173 modifiers
printf • Additional modifiers may be added between the % and the letter (in the following order) • 0 - do zero padding rather than space padding • minus sign - forces left-justification • number - minumum number of characters to output; for floats - number of digits before the decimal point • .number - for floats, the number of decimal digits modifier examples
printf printf("%5d", 3); ____3 printf("%-5d", 3); 3____ printf("%05d", 3); 00003 printf("%8f", 3.5); _______3.500000 printf("%8.3f", 3.5); _______3.500 printf("%08.3f", 3.5); 00000003.500 →
printf $mon = 4; $day = 8; $year = 2003; printf("%d/%d/%d", $mon, $day, $year); 4/8/2003 printf("%02d/%02d/%04d", $mon, $day, $year); 04/08/2003 sprintf
sprintf • sprintf formatted data and returns a string $x = sprintf("%05d", 3); print $x; 00003 print_r
print_r • print_r can be used to dump variables $x = array(1, "abc", array("covertka" => "Kent", "kingmatm" => "Tim")); print_r($x); Array ( [0] => 1 [1] => abc [2] => Array ( [covertka] => Kent [kingmatm] => Tim ) ) var_dump
var_dump • var_dump can also be used to dump variables $x = array(1, "abc", array("covertka" => "Kent", "kingmatm" => "Tim")); var_dump($x); array(3) { [0]=> int(1) [1]=> string(3) "abc" [2]=> array(2) { ["covertka"]=> string(4) "Kent" ["kingmatm"]=> string(3) "Tim" } string functions }
Useful string functions • There are many functions that can be used to manipulate strings: strlen() - string length trim(), ltrim(), rtrim() - trim strings strtoupper(), strtolower() - change case ucfirst(), ucwords() - uppercases the first character or first character of all words of a string →
Useful string functions substr() - returns part of a string strpos() - finds a substring within string explode() - splits a string into parts based on a seperator - returns an array implode() - concatenates all of the elements of an array together separated by a character →
Useful string functions str_repeat() - used to repeat a string a number of times str_pad - pads a string with another string to a particular length (left, right, or both) strcasecmp() - compares 2 strings ignoring case parse_url() - parses a URL into it's parts (scheme, host, port, path, etc.) →
Useful string functions htmlentities(), htmlspecialchars() - encodes html special characters (< > & ' ", etc.) rawurlencode(), rawurldecode(), urlencode(), urldecode() - encodes a URL regular expressions
Regular Expressions 555-1212 preg_match('/\d\d\d-\d\d\d\d/', $phone); 513-555-1212 preg_match('/(\d\d\d-)?\d\d\d-\d\d\d\d/', $phone); (513)555-1212 or (513) 555-1212 preg_match('/\(?(\d\d\d-)?\)?\s?\d\d\d-\d\d\d\d/', $phone); parse the parts into variables preg_match('/\(?(\d\d\d)?-?\)?\s?(\d\d\d)-(\d\d\d\d)/', $phone, $parts); →
Regular Expressions • The regular expression functions are used to perform various pattern matching activities: preg_match(), preg_match_all() - match (and extract) a pattern or all patterns from a string. preg_replace() - replace substrings that match a pattern with another substring. preg_split() - split a string based on a pattern. preg_grep() - find all elements of an array that match a pattern. →
Regular Expressions $x = 'abcdefghijk'; if (preg_match('/def/', $x)) { print "Found the string."; } patterns
Patterns • Patterns are enclosed within delimiters - usually slashes /def/ →
Patterns • Some characters have special meanings Matches Pattern True False . any single characters /c.t/ cat, execute coat ^ beginning of string /^cat/ cat, caterpiller application $ end of string /cat$/ cat, wildcat application | or /cat|dog/ application, dogged \b word boundary /\bcat/ cat, catalog, big cat wildcat \B non-word boundary /\Bcat/ wildcat cat, catalog →
Patterns Matches Pattern True False \s whitespace /c\st/ mac technology cat \S non-whitespace /c\St/ application mac tech \w word character (0-9,a- /c\wt/ cat, application c$t z,A-Z,_) \W non-word character /c\Wt/ c$t cat \d digit /\d\d\d/ 123, abc123def a1b2c3 \D non-digit /\D\D\D/ some text 123ab456 modifiers
Patterns • A backslash can be used to "escape" any reserved characters /c.t/ - matches c.t and also cat, cot, cut /c\.t/ - matches c.t and nothing else →
Patterns • Custom character patterns can be constructed using square brackets /c[aou]t/ - matches cat, cot, or cut, but not cet or cit • a hyphen can be used to specify a range /c[a-fu-z]t/ - matches cat, cbt, cct, or cut, cvt, czt but not cit or cot /[0-9a-fA-F]/ - matches a hexadecimal character →
Patterns • a caret after the [ indicates negation /c[^aou]t/ - matches cet, cit, but not cat, cot, or cut /c[aou^ei]t/ - can't mix - caret must be at the beginning - if not, it's treated like a caret quantity modifiers
Pattern Quantity Modifiers Matches Pattern True False * 0 or more times /ca*t/ ct, cat, caaaat cabat + 1 or more times /ca+t/ cat, caaaat ct ? 0 or 1 times /ca?t/ ct, cat caaaat ct, cat, {n} Exactly n times /ca{3}t/ caaat caaaat Between n and m {n,m} /ca{1,3}t/ cat, caat, caaat ct, caaaat times (inclusively) {n,} At least n times /ca{2,}t/ caat, caaaaat ct, cat parens
Patterns • Parenthesis have 2 purposes: • Grouping • Remembering →
Patterns • Parenthesis for grouping 555-1212 or 513-555-1212 /\d?\d?\d?-?\d\d\d-\d\d\d\d/ /\d{3}?-?\d\d\d-\d\d\d\d/ /(\d\d\d-)?\d\d\d-\d\d\d\d/ /(\d{3}-)?\d{3}-\d{4}/ →
Patterns • Parenthesis for remembering $phone = "The phone number is 555-1212."; preg_match('/(\d{3}-)?(\d{3})-(\d{4})/', $phone, $parts); print_r($parts); Array ( [0] => 555-1212 [1] => [2] => 555 [3] => 1212 ) →
Patterns $phone = "The phone number is 513-555-1212."; preg_match('/(\d{3}-)?(\d{3})-(\d{4})/', $phone, $parts); print_r($parts); Array ( [0] => 513-555-1212 [1] => 513- [2] => 555 [3] => 1212 ) →
Patterns /(\d{3})?-?(\d{3})-(\d{4})/ - allows for -555-1212 or 513555-1212 /((\d{3})-)?(\d{3})-(\d{4})/ Array ( [0] => 513-555-1212 [1] => 513- [2] => 513 [3] => 555 [4] => 1212 ) →
Patterns • A ?: following an open paren causes the paren to be used for grouping but not remembering /(?:(\d{3})-)?(\d{3})-(\d{4})/ Array ( [0] => 513-555-1212 [1] => 513 [2] => 555 [3] => 1212 ) →
Patterns • Rememberd patterns can also be referenced using \1, \2, \3, etc. /(.)(.)\2\1/ Would match - abba, toot, otto, dood Would not match - abab abaa, abbb trailing options
Trailing options • Various modifiers can be added after the trailing slash • i - ignore case /[0-9a-fA-F]/ - hexadecimal character /[0-9a-f]/i - same functions
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