PEAR/Functions/FunctionDeclaration: add extra defensive coding #1382

Job	Run time
Build Phar on PHP: 8.0	25s
Coverage: 5.4	17m 20s
Coverage: 7.2 with custom ini settings	3m 48s
Coverage: 8.3	3m 30s
PHP: 5.4	1m 24s
PHP: 5.5	4m 20s
PHP: 5.6	3m 20s
PHP: 7.0	1m 5s
PHP: 7.1	1m 1s
PHP: 7.2	1m 7s
PHP: 7.3	44s
PHP: 7.4	56s
PHP: 8.0	1m 41s
PHP: 8.1	1m 2s
PHP: 8.2	51s
PHP: 8.3	37s
PHP: 8.4	41s
PHP: 5.5 with custom ini settings	3m 47s
PHP: 7.0 with custom ini settings	57s
coveralls-finish	4s
	48m 40s

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