print_r() results in warning: unexpected NAN value was coerced to string #23662

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1. ausi

   added

   Bug

   Status: Needs Triage

   on Sep 11, 2026
2. ndossche commented on Sep 11, 2026

   

   ndossche

   on Sep 11, 2026

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   More specifically:

   <?php
   print_r([NAN]); // warns
   var_dump(NAN); // does not warn
   var_export(NAN); // does not warn
   echo NAN; // warns

   From the RFC:

   we propose to emit the following warning when NAN is coerced (be that implicitly or explicitly) to another type:

   So based on interpretation this either means that none of the above should emit a warning, or all of them should.

   This affects passing NAN as an argument to parameters which do not declare float as a type, all casting operators, logical operators, if statements, and ternary operator.

   None of the above fall into this category, so based on this none of them should emit a warning.

   It gets more confusing because of different entry points:

   <?php
   json_encode([NAN]); // does not warn
   http_build_query(['a'=>NAN]); // warns

   This seems inconsistent: I believe they should behave the same way.

   This would fix the printing case, but leaves the json/http example inconsistent:

   diff --git a/Zend/zend.c b/Zend/zend.c
   index aa621c4daa8..c5c220aed38 100644
   --- a/Zend/zend.c
   +++ b/Zend/zend.c
   @@ -521,6 +521,10 @@ void zend_print_flat_zval_r_to_buf(smart_str *buf, zval *expr) /* {{{ */
    		case IS_STRING:
    			smart_str_append(buf, Z_STR_P(expr));
    			break;
   +		case IS_DOUBLE:
   +			/* Not going through the string coercion as printing a value is not a cast. */
   +			smart_str_append_double(buf, Z_DVAL_P(expr), (int) EG(precision), false);
   +			break;
    		default:
    		{
    			zend_string *str = zval_get_string_func(expr);
   @@ -597,6 +601,10 @@ static void zend_print_zval_r_to_buf(smart_str *buf, zval *expr, int indent) /*
    		case IS_LONG:
    			smart_str_append_long(buf, Z_LVAL_P(expr));
    			break;
   +		case IS_DOUBLE:
   +			/* Not going through the string coercion as printing a value is not a cast. */
   +			smart_str_append_double(buf, Z_DVAL_P(expr), (int) EG(precision), false);
   +			break;
    		case IS_REFERENCE:
    			zend_print_zval_r_to_buf(buf, Z_REFVAL_P(expr), indent);
    			break;
   

   It is unclear to me what the intended semantics are, the RFC is underspecified.
   The real fix is probably to move the warning to the entry points of coercion rather than deep into the engine itself.
   cc @Girgias
3. Girgias commented on Sep 11, 2026

   

   Girgias

   on Sep 11, 2026

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   TBH the intention was to warn on any coercion, including to string when priting. So the echo behaviour is correct from my PoV. Now I do agree that print_r() is more a debugging function than anything else so should probably behave like var_dump().

   The reason json_encode allows NAN is that NAN is a valid value in JSON, but it is not in HTTP.
4. ndossche commented on Sep 11, 2026

   

   ndossche

   on Sep 11, 2026

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   I do find it confusing, because strictly speaking they all make a conversion to a string

   The reason json_encode allows NAN is that NAN is a valid value in JSON, but it is not in HTTP.

   This is false, NAN is not valid in JSON.
5. Girgias commented on Sep 12, 2026

   

   Girgias

   on Sep 12, 2026

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   I do find it confusing, because strictly speaking they all make a conversion to a string

   sure but var_dump is a debuging utility, and var_export is meant to export code that can be executed and NAN is a valid PHP float constant. So I don't think those should warn. The question for me is print_r a debugging function or not (IMHO yes).

   The reason json_encode allows NAN is that NAN is a valid value in JSON, but it is not in HTTP.

   This is false, NAN is not valid in JSON.

   TIL, well I guess then yes should be fixed as well.
6. ausi commented on Sep 12, 2026

   

   ausi

   on Sep 12, 2026

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   json_encode([NAN]); // does not warn
   

   This actually results in the error Inf and NaN cannot be JSON encoded, so there is probably no fix needed for json_encode(), see https://3v4l.org/Gfpeh#veol

   👍React with 👍1Reacted by Nora Dossche
7. DanielEScherzer commented on Sep 12, 2026

   

   DanielEScherzer

   on Sep 12, 2026

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   Just going to cross link #22683
8. CodedByManish

   added a commit that references this issue on Sep 13, 2026

   Fix phpGH-23662: avoid NAN warning in print_r()

   This issue will close once commit 3b9d35a is merged into the 'master' branch.

   3b9d35a
9. LamentXU123

   added

   Extension: standard

   Status: Verified

   and removed

   Status: Needs Triage

   on Sep 14, 2026
10. Girgias

    closed this as completedin 30920e9on Sep 19, 2026
11. pull

    added a commit that references this issue on Sep 19, 2026

    Fix phpGH-23662: avoid NAN warning in print_r()

    This issue will close once commit 30920e9 is merged into the 'master' branch.

    30920e9