php string-part 2

Strings
TYBSc. Comp. Sci
Chapter 2- Functions & Strings
monica deshmane(H.V.Desai college) 1

Points to learn
String
• Encoding and escaping
• Removing HTML tags
• Comparing strings

Encoding and Escaping
HTML, web page addresses, and database
commands are all strings, but they each require
different characters to be escaped in different ways.
PHP has a number of built-in functions to convert to
and from these encodings.
these encodings are placed between & and ;
“ encoded to &quote;
< encoded to <
> encoded to >
‘ encoded to '
& encoded to & monica deshmane(H.V.Desai college) 3

2 functions
1. Entity-quoting all special characters
• htmlentities(string,[quotestyle,character-
set])
2.Entity-quoting only HTML syntax
characters
• Htmlspecialchars
(string,[quotestyle,character-set])

• Entity-quoting all special characters
Ex. htmlentities($str, ENT_COMPAT);
ENT_COMPAT - convert double-quotes and leave
single-quotes as it is. This is bydefault
ENT_QUOTES - convert both double and single
quotes.
ENT_NOQUOTES - leave both double and single
quotes as it is.
ENT_IGNORE - Silently discard invalid code unit
sequences instead of returning an empty string.

Entity-quoting only HTML syntax
characters
• $str = "<html><body>John &
'Jim'</body></html>";
• echo htmlspecialchars($str, ENT_COMPAT);
• echo " ";
• echo htmlspecialchars($str, ENT_QUOTES);
• echo " ";
• echo htmlspecialchars($str, ENT_NOQUOTES);
• The browser output of the code above will be:
• <html><body>John & 'Jim'</body></html>
• <html><body>John & 'Jim'</body></html>
• <html><body>John & 'Jim'</body></html>monica deshmane(H.V.Desai college) 6

$str = "John & 'Jim'";
echo htmlentities($str, ENT_COMPAT);
echo " ";
echo htmlentities($str, ENT_QUOTES);
echo " ";
echo htmlentities($str, ENT_NOQUOTES);
The browser output of the code above will be:
John & 'Jim'
John & 'Jim'
John & 'Jim'
Select "View source" in the browser window:
John & 'Jim' 
John & ' Jim ' 
John & 'Jim'

characters
• Select "View source" in the browser
window:
<html><body>John &
'Jim'</body></html> 
<html><body>John &
'Jim'</body></html> 
<html><body>John &
'Jim'</body></html> monica deshmane(H.V.Desai college) 8

characters
• htmlspecialchars(string,quotestyle,character-set)
The htmlspecialchars() function converts some
• predefined characters to HTML entities.
• The predefined characters are:
• & (ampersand) becomes &
• " (double quote) becomes "
• ' (single quote) becomes '
• < (less than) becomes <
• > (greater than) becomes >
monica deshmane(H.V.Desai college)
9

Removing HTML tags
• Function-:
• strip_tags()
• What we require?
• String
• Which tags to allow?
• Syntax-
• strip_tags(string[, allow])

Removing HTML tags
strip_tags()
The strip_tags() function strips a string from HTML,
XML, and PHP tags.
strip_tags(string[, allow])
First parameter is the string to check,
allow is Optional that Specifies allowable tags. These
tags will not be removed.
echo strip_tags("Hello world!");
Output: Hello world
echo strip_tags("Hello world!", "");
Output: Hello world

add slashes
echo addslashes( “it’s interesting” );
Output:
“it’s interesting”
remove slashes
echo stripslashes(“it’s interesting”);
Output:
“it’s interesting”

–what require to compare 2 strings?
Str1
Str2
Syntax- $diff = strcmp($str1, $str2);
This function is used for comparing two strings. It returns a number less than 0 if str1 is
less than str2, returns greater than 0 if str1 grater than str2 and return 0 if str1 = str2
$str1= “hello";
$str2 = “HELLO";
$diff = strcmp($str1, $str2);
echo "$diff";
Output:
1
Comparing Strings
1. strcmp()

Comparing Strings
2. strcasecmp()
2. strcasecmp() –
What we require?
Syntax- $diff = strcasecmp($str1, $str2);
This function converts string to lower case then compares the value.
So output will be 0.

What we require?
Str1
Str2
No.of letters n to compare
Syntax- $comp= strncmp(str1, str2,n);
$str1= “hello";
$str2 = “heLLO";
$comp= strcmp($str1, $str2,2);
echo "$comp"; //true
4.Strncasecmp //same as strncmp()
Comparing Strings
3. Strncmp()

1) soundex()
2) metaphone()
Syntax –
if (soundex($str) == soundex($str2)){}
if (metaphone($str) == metaphone($str2)){}
Comparing Strings 5. Approximate equality

1) soundex() - Soundex keys produce the same soundex key according to pronunciation,
and can thus be used to simplify searches in databases where you know the
pronunciation but not the spelling.
$str = “weather";//know, our, son
$str2 = “whether"; //no, hour, sun
if (soundex($str) == soundex($str2))
{ echo "Similar";
}
else
{ echo "Not similar";
}
//Similar

2)metaphone() - Similar to soundex() metaphone creates the same key for similar sounding
words. It's more accurate than soundex() as it knows the basic rules of English pronunciation.
The metaphone generated keys are of variable length.
$str = “weather";//know, our, son
$str2 = “whether"; //no, hour, sun
if (metaphone($str) == metaphone($str2))
{ echo "Similar";
}
else
{
echo "Not similar";
}
//Not Similar

- function returns the number of matching characters of two strings. This function also
calculate the similarity of the two strings in percent.
What we require?
Str1
Str2
Percent of similarity
Syntax-:
similar_text(str1,str2,percent);
Comparing Strings 6. similar_text()

echo "Number of character matching : ".similar_text("Hello World","Hello Welcome",
$percent);
echo " Percentage : ".$percent;
Output:
Number of character matching : 8
Percentage : 66.666666666667
Comparing Strings 6. similar_text()

- function returns the Levenshtein distance between two strings.
The Levenshtein distance is the number of characters you have to replace, insert or delete to
convert string1 into string2.
What we require?
Str1,
Str2
Syntax-
$diff= levenshtein(str1,str2);
Ex.
echo levenshtein("Hello World","ello World");
//1
Comparing Strings 7. levenshtein()

Revise string
comparison functions-
1. Strcmp()
2. Strcasecmp()
3. Strncmp()
4. Strncasecmp()
5. Approximate equality
1. soundex()
2. metaphone()
6. similar_text()
7. levenshtein ()

End of Presentation

php string-part 2

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php string-part 2