String in Php

Introduction

• The string is the core-components part of Php for creating and manipulating strings in various ways.

Definition

• A string is a sequence of characters of arbitrary length.

Characteristics

• String literals/contents are denoted by either single or double quotes. For example – ‘Employee’ or “Employee” or “512” or ‘512’.
• To check whether two strings are equal, the == (double equals) comparison operator is used.
• String Escape Sequence :
  • Double quotes symbols are also used in a variety of string escapes to insert special characters in the program.
    
  • Escape Sequence – Character Represented

\”   –  Double quotes
\n – New Line
\t   – Tab
\\   – Backslash
\$ –  Dollar sign
\{   –  Left brace
\}   –  Right brace
\[   –  Left bracket
\]   –  Right bracket

• String Concatenation Operator :
  • The concatenation operator appends the multiple operands as one string value. 
  • For example – 

• String Printing in Php :
  • There are four ways to print strings in Php. These are –
    • echo statement :
      • Echo is considered a language construct (not as a true function) hence, echo can be used without the () symbol.
      • Due to construct, it can’t be used with an if statement.
      • Print single or multiple string output at a time.
      • For example – 
        • echo “India”;
        • echo (“India”);
        • echo “First”, “Second”, “Third”;    [Output: FirstSecondThird]
        • echo (“First”, “Second”, “Third”);    [Output: Parse Error]
    • print() statement :
      • Print only one string output at a time.
      • Due to function, it can be used with an if statement.
      • For example – 
        • print “India”;   [Output: Parse Error, due to print is a function & needed ( )]
        • print(“India”);  [Output: India]
        • if (print(“Yes”)) { echo “We are Indian”;}
        • print(“First”, “Second”, “Third”);    [Output: Parse Error, due to multiple outputs]
    • printf() statement :
      • This statement prints a formatted string by inserting a value by substituting the value into a template similar to C.
      • printf(“%6d\n”,7);
        printf(“%3d\n”,7);
        printf(“%03d\n”,7);
        printf(“%.2f\n”,453.21546);
        printf(“%.2f\n”,453.21246);
        printf(“%.3f\n”,453.21546);
        printf(“%.5f\n”,453.2);
        printf(“The hexadecimal value of %d is %x\n”, 300,300);
        printf(“%04d-%04d-%d\n”,05,11,2025);
        printf(“The interest amount is %.3f%%\n”,25.32);
        printf(“I\’ve %d rupees\n”,2500);
        printf(“\”The total amount is\” %d rupees”,2500);

Output:

               7
     7
007
453.22
453.21
453.215
453.20000
The hexadecimal value of 300 is 12c
0005-0011-2025
The interest amount is 25.320%
I’ve 2500 rupees
“The total amount is” 2500 rupees 

• • print_r() statement :
    • Print the contents of arrays, objects, and others in more or less human-readable form.
    • It is useful for debugging purposes.
  • sprintf() statement:
    • The sprintf() function helps in writing a formatted string.
    • Example:
      • $num = 1947;
        $str = “India”;
        $val = sprintf(“%s became free in %u year.”,$str,$num);
        echo $val;   //Output: India became free in the 1947 year.
      • $num = 15;
        $str = $num;
        $val = sprintf(“The Decimal value of %d is %b.”,$num,$str);
        echo $val;     //Output: The Decimal value of 15 is 1111.

In-built String Function in Php

• PHP has several in-built functions regarding string to compare, search, replace, and trim strings, for working with HTTP, HTML, and SQL encodings. Some common in-built string functions are –
• is_string():
  • An in-built function is_string() is used to test whether a value is a string. The syntax is -(is_string($String_variablename)).
• bin2hex():
  • This function converts a string of ASCII characters into hexadecimal values. 
  • Syntax: bin2hex(string)
  • Example: echo bin2hex(“Hello India”);     //[Output: 48656c6c6f20496e646961]
• chr():
  • This function returns a character from the specified ASCII value. The ASCII value can be specified in decimal, octal, or hex values. Octal values are written by a leading 0, while hex values are written by a leading 0x.
  • Syntax: chr(ascii value)
  • Example: 
    • echo chr(56) ;   // decimal value   [Output: 8]
    • echo chr(041) ;   // Octal value [Output: !]
    • echo chr(0x48);    // Hex value  [Output: H]
• echo():
  • This function displays the output.
  • echo is not actually a function hence no () symbol is used.
  • echo is faster than print() function.
  • Syntax: echo variable_name/string_message.
  • Example:
    • echo “Hello India”;
    • echo ‘Our ‘,’India ‘,’is ‘,’Great ‘;   //[Our India is Great]
    • $str=”Hello India”;

    echo $str;

• md5():
  • This function converts or encrypts the given string in hash form [in binary or 32-bit hex format] using RSA security algorithm.
  • Syntax: md5(string_name/string_variable)
  • Example: echo md5(“Hello India”);     //Output: 6ad0525bedec9965301c0c5e51f64a92
• nl2br():
  • This function helps to insert new line or break the line where \n present in a string.
  • \n works with this function.
  • Syntax: nl2br(string1 \n string2 \n string n)
  • Example: echo nl2br(“Welcome \n 2023”);
• ord():
  • The ord() function returns the numeric ASCII value of the first character of a string.
  • Syntax: ord(string)
  • Example: echo ord(“Hello India”);      //Output: 72    
• print() & printf():
  • Mention in the above paragraph.
• strcmp():
  • This function compares two strings and gives result as a numeric value. If it is 0, strings are equal and if greater or less than 0 are not equal.
  • It is case-sensitive.
  • Example:
    • $str1=”India”;
      $str2=”India”;
      $str3=”America”;
      $str4=”india”;
      echo strcmp($str1,$str2).”<br>”;     //Output=0
      echo strcmp($str1,$str3).”<br>”;    //Output=8
      echo strcmp($str1,$str4).”<br>”;    //Output=-32
  • strcasecmp() is similar as strcmp() but not case sensitive.
  • strncmp() is similar to strcmp() but compares up to n length and is case sensitive whereas strncasecmp() is not case sensitive.
• strlen():
  • This function is used to find out the length/characters of a string including space.
  • Syntax:
    • strlen(string_value/string_variable).
  • Example:
    • echo strlen(“Hello India”);        //  [Output: 11]
    • $x=”Hello India”;

• str_pad():
  • This function adds some extra characters as Pad to the right side of the string, up to a new length as per need.
  • Example:
    • $str = “Hello India”;
      echo str_pad($str,23,”N”);  //Output: Hello IndiaNNNNNNNNNNNN
• strpos():
  • This function is used to search for a specific word/text from a sentence or string. If a match occurs, it gives the character position as the index value of the first match. If no match is found, it returns FALSE.
  • The position counting starts from the beginning/first letter of the string taking index value 0, not from 1.
  • Syntax:
    • strpos(string_value/string_variable, search_text).
  • Example:
    • echo strpos(“Hello India”, “India”);        //  [Output: 6]
    • $x=”Hello India”; 

    echo strpos(x, “India”);        //  [Output: 6]

• str_replace():
  • This function replaces some characters with some other given characters in a string.
  • This is case sensitive function.
  • Another function is str_ireplace() which is not case-sensitive.
  • Syntax:
    • str_replace(find_letter, replace_letter, string_sentence);
  •  Example:
    • echo str_replace(“India”, “World”, “Hello India”);  //[ Output: Hello World]
• strrev():
  • This function is used to reverse a given string.
  • Syntax:
    • strrev(string_value/string_variable).
  • Example:
    • echo strrev(“Hello India”);        
    • $x=”Hello India”;

   strrev($x);   

• strstr():
  • This function replaces certain characters or words from a string.
  • It is case-sensitive.
  • Example:
    • echo strstr(“Hello India” “India” “World”);      //Output: Hello World
    • echo strstr(“Hello India” “i” “o”);     //Output: Hello Indoa
    • $arr2 = array(“Hello” => “Our”, “World” => “Universe”);   // In Array
      echo strtr(“Hello World”,$arr2);     //output: Our Universe
• strtolower():
  • This function converts all characters to lowercase letters.
  • Example:
    • echo strtolower(“Hello INdiA.”);   //output: hello india
• strtoupper():
  • This function converts all characters to uppercase letters.
  • Example:
    • echo strtoupper(“Hello INdiA.”);   //output: HELLO INDIA
  • NB: 
    • lcfirst() – This function converts the first character of a string/sentence to lowercase letters.
    • ucfirst() – This function converts the first character of a string/sentence to uppercase letters.
    • ucwords() – This function converts the first character of each word in a string/sentence to uppercase.
• str_word_count():
  • This function counts the total number of words present in a string/sentence.
  • Syntax:
    • str_word_count(string_value/string_variable).
    • Example:
      • echo str_word_count(“Hello India”);        
      • $x=”Hello India”;

     str_word_count($x); 

• substr():
  • This function extracts part of the string as per the given position value.
  • Example:
    • echo substr(“Hello India”,6)    //output: India
    • echo substr(“Hello India”,9)    // output: ia
    • echo substr(“Hello India”,-3)    // output: dia
    • echo substr(“Hello world”,-8)    // output: lo world
    • echo substr(“Hello world”,3,8)    //output: lo wo
    • echo substr(“Hello world”,0,5)    // output: Hello
    • echo substr(“Hello world”,7,7)   //output: orld
    • echo substr(“Hello world”, 0,-6)   //output: Hello
    • echo substr(“Hello world”,-10,-4)    //output: ello w 
• trim():
  • This function removes extra whitespace [null, new line, horizontal tab, vertical tab, space etc.] from both sides/ends of the string.
  • Syntax: trim(string_name/string_variable)
  • Example: echo trim(”      Hello India    “);     //Output: Hello India
  • NB: rtrim() and ltrim() function removes extra whitespace from the right side and left side of the string.