Why doesn't this code simply print letters A to Z?

<?php
for ($i = 'a'; $i <= 'z'; $i++)
    echo "$i\n";

This snippet gives the following output (newlines are replaced by spaces):

a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd 开发者_StackOverflow社区be bf bg bh bi bj bk bl bm bn bo bp bq br bs bt bu bv bw bx by bz ca cb cc cd ce cf cg ch ci cj ck cl cm cn co cp cq cr cs ct cu cv cw cx cy cz da db dc dd de df dg dh di dj dk dl dm dn do dp dq dr ds dt du dv dw dx dy dz ea eb ec ed ee ef eg eh ei ej ek el em en eo ep eq er es et eu ev ew ex... on to yz

From the docs:

PHP follows Perl's convention when dealing with arithmetic operations on character variables and not C's.

For example, in Perl 'Z'+1 turns into 'AA', while in C 'Z'+1 turns into '[' ( ord('Z') == 90, ord('[') == 91 ).

Note that character variables can be incremented but not decremented and even so only plain ASCII characters (a-z and A-Z) are supported.

From Comments:-
It should also be noted that <= is a lexicographical comparison, so 'z'+1 ≤ 'z'. (Since 'z'+1 = 'aa' ≤ 'z'. But 'za' ≤ 'z' is the first time the comparison is false.) Breaking when $i == 'z' would work, for instance.

Example here.

Because once 'z' is reached (and this is a valid result within your range, the $i++ increments it to the next value in sequence), the next value will be 'aa'; and alphabetically, 'aa' is < 'z', so the comparison is never met

for ($i = 'a'; $i != 'aa'; $i++) 
    echo "$i\n"; 

Others answers explain the observed behavior of the posted code. Here is one way to do what you want (and it's cleaner code, IMO):

foreach (range('a', 'z') as $i)
    echo "$i\n";

In response to ShreevatsaR's comment/question about the range function: Yes, it produces the "right endpoint", i.e. the values passed to the function are in the range. To illustrate, the output from the above code was:

a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z

Others already said why PHP doesn't show what you expect. Here's how you get the result you might want:

<?php
for ($i = ord('a'); $i <= ord('z'); $i++)
    echo chr($i);
?>

Why not just use range('a','z')?

Try this code. I think this code will be helpful to you.

$alphas = range('A', 'Z');
foreach($alphas as $value){
    echo $value."<br>";
}

Display 26 letters in sequence.

<?php

$i = 'a';
do {
echo ($j=$i++),"\r\n";
} while (ord($j) < ord($i));

?>

Also this can be used:

for ($i = 'a'; $i <= 'z'; $i=chr(ord($i)+1))
    echo "$i\n";

PHP has the function of looping letters and can exceed beyond single characters; the rest will be done this way: aa ab ac... zz, and so on.

Try this:

<?php
for ($i = 'a'; $i !== 'aa'; $i++)
    echo "$i\n";
?>

While the above answers are insightful to what's going on, and pretty interesting (I didn't know it would behave like this, and its good to see why.

The easiest fix (although perhaps not the most meaningful) would be just to change the condition to $i != 'z'

<?php
for ($i = 'a'; $i != 'z'; $i++)  
    echo "$i\n";
?>

The PHP does not consider 'AA' less than 'Z'. The best way to make this is:

for($i = 'a'; $i != 'aa'; $i++) {
  echo $i;
}

abcdefghijklmnopqrstuvwxyz

Perhaps this code will work. It’s easy & can be understood:

<?php
$ascii_val = ord("a");
for($i=$ascii_val;$i<$ascii_val+26;$i++){
echo chr($i)."\n";
}
?>

where 26 is the total number of letters in the alphabet.

There are several ways to do that.

1. First you can take the range from 'a' to 'z'. Then iterate a loop over it.

foreach(range('a', 'z') as $i)
{
    echo $i . "\n";
}

2. You can print the letters using asci value of the characters.

for($i = 97 ; $i<=122; $i++)
{
  echo chr($i) . "\n";
}

3. You can take the asci value of 'a' and run a loop till the asci value of 'z':

for ($x = ord('a'); $x <= ord('z'); $x++)
{
    echo chr($x) . "\n";
}

4. For printing a new line in html you can append the
to the end of each characters.

for($i='a';$i<='z';$i++)
{
    echo $i. "<br />"; 
}

this code will work. It’s easy & can be understood:

<?php


// print form A to ZZ  like this
// A B C ... AA AB AC ... ZA .. ZZ
$pre = "";
$i = ord('a');
for ($x = ord('a'); $pre . strtoupper(chr($x-1)) != 'AH'; $x++)
{
    echo "". $pre . strtoupper(chr($x)) . "\n";

    if(chr($x) === "z"){
        $pre = strtoupper(chr($i++));
        $x = ord('a');
        $x--;
    }
}

One more way to get the display of characters a-z:

<?php
 for ($i = 'a'; $i < 'z'; $i++){
     echo "$i\n";
 }
 echo $i;  // 'z'

See live code Once the conditional loop becomes false, $i will have already been incremented and have the string value corresponding to 'z' which can be displayed.

Wow I really didn't know about this but its not a big code you can try echo "z" after loop Mark is Absolutely Right I use his method but if you want alternative then this may also you can try

<?php
for ($i = "a"; $i = "y"; $i++) {
    echo "$i\n";
    if ($i == "z") {}
}
echo "z";
?>