Curious about Output of printf

Question

Hello today I was reading about printf in PHP. printf outpust a formatted string. I have a string. I was about to format the floating point string like

 $str = printf('%.1f',5.3);

I know about format %.1f means. Here 1 is number of decimal places. If I echo $str like

echo $str;

It outputs

5.33

I can understand the output because 5.3 is the string and 3 is the lenght of outputed string which is the return value of printf.

But see my following code

$str = printf('%.1f', '5.34');
echo 'ABC';
echo $str;

It outputs

5.3ABC3

I wonder how it is happening? If we go simple PHP interpolation it should output ABC first then it should output 5.33 because we are formatting only 5.33 not ABC.

Can any one guide me what is happening here?

ABorty · Accepted Answer · 2013-06-12 08:11:06Z

5

Place echo "<br>" after every line.You will understand how it is happening.

$str = printf('%.1f', '5.34');    output is 5.3
echo "<br>";
echo 'ABC';    output is ABC
echo "<br>";
echo $str;    output is 3

answered Jun 12, 2013 at 8:11

ABorty

2,5121 gold badge15 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Sarwar Hasan · Accepted Answer · 2013-06-12 08:34:07Z

3

printf is like a echo command.It display output by itself and it returns length of string which it is displayed.

if you want to get the output into a variable then you need to add

$str=sprintf('%.1f',5.3);
echo 'ABC';
echo $str; 
// now the output will be "ABC5.3

Thanks

answered Jun 12, 2013 at 8:34

Sarwar Hasan

1,6412 gold badges18 silver badges27 bronze badges

Comments

Baba · Accepted Answer · 2013-06-12 07:54:50Z

1

printf would Output a formatted string and returns the length of the outputted string not the formatted string. You should be using sprintf instead

$str = sprintf('%.1f',5.3);

The reason for 5.3ABC3

 5.3  ----------------  printf('%.1f', '5.34'); and $str  becomes 3 
 ABC  ----------------  echo 'ABC';
 3    ----------------  length of 5.3 which is $str

answered Jun 12, 2013 at 7:54

Baba

95.3k29 gold badges172 silver badges222 bronze badges

2 Comments

Awais Qarni Over a year ago

I am asking the reason of above output dear?

Baba Over a year ago

3 is the length of that was returned from printf

Mark Baker · Accepted Answer · 2013-06-12 07:56:57Z

1

$str = printf('%.1f', '5.34'); // outputs '5.3' and sets $str to 3 (the length)
echo 'ABC';                    // outputs 'ABC'
echo $str;                     // outputs the value of $str (i.e. '3')

hence

'5.3', then 'ABC' then '3'

giving

5.3ABC3

answered Jun 12, 2013 at 7:56

Mark Baker

213k34 gold badges354 silver badges390 bronze badges

2 Comments

Awais Qarni Over a year ago

But Why 5.3 first then ABC and then 3? I know the mechanisim but according to code it should be ABC5.33?

Mark Baker Over a year ago

Because printf() generates output (in your case, the value '5.3') as well as setting a variable value... it effectively does an echo itself... "Output a formatted string".... you're executing the printf() as your first line, so it's the first output sent to php://output

Andreas · Accepted Answer · 2013-06-12 08:03:26Z

1

You gave the answer yourself: printf outputs a formatted string and returns the length of the string.

So:

$str = printf('%.1f', '5.34'); // prints 5.3
echo 'ABC';                    // prints ABC
echo $str;                     // prints 3

Which altogether is: 5.3ABC3

answered Jun 12, 2013 at 8:03

Andreas

5,63710 gold badges48 silver badges57 bronze badges

Collectives™ on Stack Overflow

Curious about Output of printf

5 Answers 5

Comments

Comments

2 Comments

2 Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

2 Comments

2 Comments

Comments

Related